Problem with theme, excert

Hi everyone,
i’m using the Twenty ten theme on my blog and i want to make appear excerpts of the posts when i open the blog and not the entire post. i search and i found the php function the_excerpt();
my questions are:
my theme allows me to use excerpts without this php function?
to use these function i need to be more than a free user?
there is any free template by wordpress that allows me to use this option?

thanks