Help please

I have already been to my blog that was included with my website… I changed the name of it from the demo to TTY-Designs zoofully blogging… it’s been a few weeks & I wanted to go & see other templates I could use… it said I needed to register when I went… so I did… then when I get logged in & it does take me to the admin area that I click on but in there when I click on change my site theme it says >> You do not have sufficient permissions to access this page.<<

help please… ty in advance