Hello… sorry for my english but i’m a n00b!
i would like to know… where can i find some plug-in to have the effect of an auditorum or a studio record?
i’ve tried to register a song with audacity but i would like to make it more professional 
For an “auditorium” effect, install some plug-ins (see the main the Audacity web site) and use “G-verb” or “FreeVerb”. You will be able to get echoey sounds from these.
Like a “studio record” is a bit like saying “I got a guitar for Christmas, how do I get it to sound like Steve Vai?”
Do lots of reading, studying and practicing, then upgrade your hardware as and when you need to.