i have downloaded the average xp bar addon but when i go o the addons button it tells me that it is incompatible.Does anybody know what i can do to solve this problem? thank you

You got an addon that was not updated for the new patch. Get ones that were updated between January and now.

but all of my addons do not work

First, check the box at top that says load out of date addons. If your mods are still colored red, mouse over them to see what the error is. If it says incompatible, you need to delete those mods. Download only mods with dates later than mid december. Old Lua 1.0 mods (mods from before TBC) will not work with today's current WoW.