Actually JeanetteIsabelle is right. You could leave messages somewhere they are going to be found. After all you know what is going to surivive. I've seen the Book of Kells myself. Or get the church to pass the message on. You know London is going to be built up miles from where it is now. Just burying plenty of messages anywhere near and some will be found.
There was an iteresting twist on this in a short story where someone leaving a time capsule is approached by a mysterious stranger saying he wants to discover if they will have time travel in the future, by leaving messages in time capsules, claiming to be transcribed from a traveller from the future, too sick to write himself and asking to be rescued. Transcribed because of course the person really leaving the note doesn't know the language of the future.
"But what if a traveller from the future really did want to be rescued?" asked the time capsule man; "how would he persuade people leaving time capsules to include messages?"
"I'm sure he'd think of something" says the stranger.

But as you say JeanetteIsabelle is also missing the point. This is a survival site; we are interested in how we'd manage without our technology (he says after including a science fiction story precise).
I think we'd be lost; so you know radios and cars will be possible one day? Can you make one?
Being able to read and write and do arithmetic could make you a town record keeper. If you could persuade them to let you keep it in your own language while you learnt theirs.
The need for hygiene would probably be your greatest knowledge. Setting up as a doctor who at least didn't use snails and handle wounds with filthy fingers could bring results. Again if you last long enough to learn their lingo.
Do you think the only piece of technology I could introduce; the button, would make me rich? :-)
The Sock