I have a web page www.yuckyhousetraining.com

i cant see where to go in the HTML editor to get the page centered and at about 700 width. I have gone through posts here but i dont understand everyones ans.

some say to put a code in and upload to css file, others say put this code in, but i dont know where to place it?

One of the problems with my page is it was created in a paid members site- but i dont want to use that place anymore. so all i did was copy and paste the page- and it showed up- pictures and all- so i have no pictures on the server... i have no real "files" is this going to be a problem when i cancel that other site?