How to start the process of GC

Hello everyone,

I am a programmer in USA now,and I have asked my boss to apply employee based GC. However,both my boss and I have no idea how should we start and what we need to do in the whole process. Yes, I know I need a lawer to help me,but my boss insist that we should know the process first.
BTW, I am H1 3th year,and the company I am working has an employee size of 55,and I am the only non-citizen of USA.

Please advice. Thanks.