After I buy a head texture, create my head, how do I
put it on to make a new head?

you hit edit on the head texture item in your inventory then click choose file, and choose your head texture picture(that you created) and hit upload.

One thing that confuse me, where is my inventory?

press that button shop at top press deactivated or activated

I tried to upload it but it didn't work.
is there something I could make it work?

What is the file format of the picture you used?

the file format is shown by the file name ie picture.png

png would be that file's file format

Didn't want to make a new post for my issue cause I think it's related !

I wanted to change my head texture because I was being bored of my old one =p, so yeah I made new one and when I try to upload it a message shows up :
"You need to purchase the dq.wav from the shop in order to upload"

and my texture won't upload, there's no thumbnail. When I try to upload it from the textures list (and not from my inventory) it says "upload done" or something like this, but it obivously fails D:

Try a different file format, like .png or .gif.

I tried both .jpg and .png. I'm goin to try .gif and see what happens.

EDIT : I tried .tga and .gif. no changes... D: