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Rider, I believe the functions you're looking for are not an option for you. I'm not sure exactly what tier it is, but you should probably ask a staff member via VM how much you'd have to donate to get the ability to implement background images in your profile. You CAN customize your profile, just look for the "Customize Profile" link on your own profile, but you are limited to colors only, and not images.
As for the Youtube video, you should go to http://www.pokecommunity.com/profile.php?do=editoptions
and scroll down to the bottom. There's a box called "Youtube URL" Take the LAST PART of the URL, the "v=" parameter, particularly what's after the v= and copy it. Next type '/v/' into the box and THEN paste the video id that you copied, that's the part after the 'v=', in after the /v/
Your link should look like this: /v/sZPvp-HRRYQ
Scroll down a bit more to the "Swap Video" option and make sure the "Yes" radio button is selected.
Hit "Save Changes"
Next you should go to http://www.pokecommunity.com/profile.php?do=editprofile
Scroll down to the "YouTube Video Title" field there and copy pasta the video title if you want to and fill out pertinent information. This is helpful if you decide to do something like turn off the "Swap Video" option I mentioned above to get it off the top of your profile, as it will put your video in the side bar if you do.
The second optional step is to scroll down to the "YouTube Video FMT (Quality)" box and make a choice. Enter 18 for normal quality, 22 for medium quality and 35 for highest quality available. (35 results may vary because it uses the HIGHEST quality offered on the video, and videos sometimes don't have high quality versions.