I had no idea you could poison arrows, how do you poison arrows?

I'm new to this game and would like to know as well. (bump)

you poison your bow, not your arrows

You can't, you poison the bow. Just when you find/make a poison, use it when you have a bow equipped and it will ask you if you want to poison the bow.

1. Buy or craft a poison.
2. Equip a weapon (bow, in this case).
3. Use a poison the same way you'd use a potion.
4. A window pops up asking if you want to apply posion to your weapon - click yes.

Pretty simple, and yields very nice results.

Isn't it single use though, so you need to re-apply the poison each time you want to use it?

yes

Btw the poisons are single use only (unless you have an alchemy perk). Incase you meant you could re apply the same poison.