okay how do u do them, are there any other instruments you can fo them on other then flutes and i think clarinets

Any instrument can trill. How fast the trills are, and if there are any two given notes where it's impossible will differ, but the effect is entirely possible on anything (yes even on trombone). Trills depend on what exactly the notation is. If it's just the normal trill sign (usually a horizontal squiggly line over the note to be trilled), you go up to the next step in the key. For example, in the key of Bb, if you were trilling on an Eb, you'd go to F, not E (Fb). If, however, there is a flat sign next to the squiggly line, you trill between the written pitch, but bring down the what the other pitch would be if there were no flat sign by half a step. On that same Eb in the key of Bb, if there's a flat sign, you trill from Eb to E, rather than Eb to F. If there is a sharp sign, you raise the unwritten pitch a half step, so the Eb to F trill becomes and Eb to F# trill. A trill is just a rapid repetition between two notes, and can be performed at varying speeds as the music calls for it.

Also although there are obviously short cuts for when you trill to make the more awkward fingerings less dificult, and they're not too bad if you do a bit of practise. Anything is possible if you do a bit of work!