The Outfit window is where you can create new outfits, edit an outfit or delete an outfit. You can open the Outfit window by clicking on the Outfit button at the bottom of the screen.
To create a new outfit, first go into the Outfit window by clicking on Outfit at the bottom of the screen, then at the top of the Outfit window, click on Create New Male or Female.
When you click on one of these, a pop up will appear asking you to name the outfit. Once you have named it, click on OK to create the outfit. This will give you a default avatar which is customisble. You can see which outfit is active by opening the Outfit List (the active outfit will be in grey).
The Copy ID button can be ignored; this is generally used for developers who want to use their live outfits to make NPCs.
Other than creating new outfits, there are a few more options along the top of the Outfit window.
Save As - You can have any outfit active, and after customising it, you can then choose to Save As to save it as a separate outfit with a different name.
Delete - This will delete the current active outfit. Only click this if you are really sure you want to delete the outfit, as you won't be able to restore it.
Outfit List - This is where you can see a full list of all the outfits you have made.
Refresh List - If you make a new outfit and it doesn't show up on the list, you can click on refresh to refresh the list and it should show the new outfit listed.
There are a lot of customise options for avatars in the Outfit window; You can change what clothing your avatar is wearing, choose a preset, customise the head and body, change the skin or use morphs. You can find all these options down the left-hand side of the Outfit window.