Navigation using the stars is actually reasonable simple and it very simple to get a Latitude position and with a reasonable degree of accuracy. Longitude measurement is slightly more difficult.

Firstly find the star called Polaris. Polaris is easy to find. Polaris always points north if you are in the northern hemisphere. Get your compass out from your PSK and look upwards in the northerly direction. In the northern hemisphere all the other stars rotate around Polaris over the course of the night. A quicker method is to find Ursa Major (Great Bear or as in the UK referred to as the Plough) and then locate the star Merak (the front corner of the plough's blade). In this constellation the nearest brightest star will be Dubhe. Follow the imaginary line these two stars make and here you find the next brightest star in sequence called Polaris. Merak and Dubhe will point to the star Polaris. Once you know how to find the star Polaris using this method you don't even need a compass to start off with.

Secondly to determine you Latitude you just measure then angle or angular separation between the horizon and the star Polaris. To do this you need a sextant. Point the telescope viewer or iron sight of the sextant at the star Polaris and read of the angle. This is your Latitude.
Even a simple bush craft made sextant will get you within + or - 100 miles approximately either way of your true Latitude. A bubble indicator from a spirit level is always handy to have in your PSK together with your hacksaw blade. The bubble indicator will allow the bush craft sextant to be level with the horizon if the horizon is difficult to determine in the dark. The hack saw blade will allow you mark of the ratios of 3,4,5 so as to give you a right angle triangle, which will then give an accurate angular reference measurements of 36.87 and 53.13 degrees. These reference angles can then be accurately subdivided into smaller angles and will allow the construction of a reasonably accurate bush craft sextant. Achievable accuracy could be + or – 1 degrees.

Since accurate time and global navigation were invented in Britain due of the invention of the chronometer or pocket watch by Harrison (Known as H4) in the late 17th century, the reference angle of 0 and 360 degrees is set to the imaginary north south line called the prime meridian which bisects the globe through Greenwich in London.

Longitude is much more difficult to determine as this will require an accurate timepiece, which is set to Greenwich Mean Time or is at least referenced to Greenwich Mean Time GMT or UTC (otherwise known as Universal Time Co-ordinate) and something called a solar ephemeris table.
By measuring the referenced time of the sunrise and sunset together with the time of year and the measured latitude then by looking up the solar ephemeris table a reasonable measurement of latitude can be derived.
Generally having an accurate timepiece is not really a problem especially with today’s modern quartz regulated watches. (It may surprise some that the British Harrison H4 which is over 250 years old will actually keep better time than most contemporary Japanese and Swiss timepieces). Having a solar ephemeris table is not something that most people would have access to in the wilderness.

A simpler less accurate method is to measure the time of the suns zenith (the point at which the sun is the highest in the sky at the longitude to be determined). This can be done using a bush craft sundial. Improved accuracy can be achieved by the use of averaging the time of the each daily sun’s zenith time results.

1 day’s rotation of earth = 360 degrees = 24 hours
15 degrees = 1 hour
1 degree = 1/15th hour = 4 minutes (this will be accurate to again + or – 60 miles approximately)

Measuring the difference in time between local noon and Greenwich noon made it possible to determine longitude. If local noon was 6 hours after Greenwich noon, the latitude will be 90 degrees (6* 15) west of Greenwich.
Because the earth rotates once per day, any given point on the earth's surface travels through a circle of 360 degrees once every 24 hours. Thus, each hour, a given point travels through 15 degrees of longitude (360/24). To determine one's longitude, one compares the time of local noon (when the sun is at its highest point) to the time of noon at a place with a known longitude. The difference in time is converted to the difference in longitude with a fairly simple calculation.
For example, if one hour is equal to 15 degrees, then 6 hours would equal 90 degrees, and 6 hours and 30 minutes would be 97.5 degrees.
If the local sun’s zenith can be fixed within 4 minutes then the location of the longitude to be measured will be between + or – 60 miles approximately of the true longitude.