Most workers have to wait for their priority date to be come current before they are allowed to file their I-485 Adjustment of Status Petition.
The USCIS will not accept your I-485 Adjustment of Status Petition until your priority date is current.
The priority date is the date the DOL received your Labor Certification (PERM) or I-140 Petition.
You can check the Visa Bulletin Here: http://travel.state.gov/visa/frvi/bulletin/bulletin_1360.html., and here.