I think when you said 'packets' you meant 'packages' thats what programs (with their sources and documentation) are called in linux.
what distro are you using? Mara, the fine Mod is right it does matter which one your using, but it probably is just 'startx'
however, that may just print out garbage (error message) if your monitor and such are incorrectly set up (happened a few times to me in slackware 8.0) again, depends which distro you are using.
if this is your first time setting up linux, go with mandrake or redhat, as their installs are very easy and i believe both of them (correct me if im wrong) have to option to start the computer at the GUI login screen (i know redhat does, its just a simple checkbox durning the install) im sure mandrake is close to the same. What that is actually doing is setting the default runlevel to 5 (gui mode) rather than 3 (text mode) (some distros are 4 for gui i think, but you get the idea.
let us know if you need anymore help