Well, I think the best way to start out is yeah.. you have it installed, now read as much as you can, from linux related websites or open source sites, you can try out sites like
http://sourceforge.net ,
www.linuxnewbie.org ...etc. Also it wouldn't hurt to pick up a book so you have it for a reference type manual near by, I think it also be good to get maybe a book that is distro specific on whatever your using.