I have a blog with hosting at WordPress.com: http://wildstate.ro with Piano Black Theme and I got WordPress Premium but I can’t upload my own theme or customize Piano Black like a larger header, moving menu bar, change subsol ending of the blog, larger site area and other things. How can I solve this?
There is no upgrade on wordpress.com that will allow you to upload your own themes or install plugins. You would need a self-hosted wordpress.org install to do that. Here’s a bit of info on the difference: .com and .org