how can i get a administrative account?

Answer 1

Ask your system administrator if the computer is shared, if its yours, you should have an administrator account, just backup everything and do a clean reinstall, sometimes this is a good choice, since it will also rid your computer of all the bad stuff its sure to have collected.

Answer 2

if you are a minor you will have to asked your parents. and they will probably tell you no because as an administrator you have more access to different things. if you are not a minor then asked the person who owns the computer to make you one