Once you got there, start a new topic. Post your pictures in the thread by clicking the little "picture" icon, directly below and just a bit to the left of the smiley face. A box will pop up and you need to put the url of the picture into the line provided.
1. press start press Y send to facebook(have to link facebook)
post on forum? just post reply (add picture)
Not a stupid question, really. If you don't know how to take the pictures of your world, refer to Hidden_Legaciez's comment.
If you have that done, then go here: http://www.minecraftforum.net/forum/215-mcx360-creations/
Once you got there, start a new topic. Post your pictures in the thread by clicking the little "picture" icon, directly below and just a bit to the left of the smiley face. A box will pop up and you need to put the url of the picture into the line provided.
After you've created the topic, send a personal message to this guy: http://www.minecraftforum.net/user/1800128-tjmastercrafter/
(Be sure to include a link to your newly created topic.)
That's it! Good luck!