How to change my tumblr theme?

[Natalie]

I seem to be able to do all the html workings and that for things like cursors and icons and stuff but I can't find anything that actually tells me what part of the html to delete/replace. I also can't figure out how to make my own theme, as I wish to use a picture from my own computer as my background.
Thanks in advance.

[Kalpit]

go to http://filesdownloadhelp.blogspot.in/201...theme.html