Step 1) Go to the ULS database and do a search for your license: http://wireless2.fcc.gov/UlsApp/UlsSearch/searchLicense.jsp
Step 2) When the next screen comes up with a match, click on your callsign.
Step 3) Write down the FRN Number. It is right above your name.
Step 4) Scroll down towards the bottom of the page and on the line that says ULS Online Systems
, click on ULS Online Filing
Step 5) Enter your FRN from Step 3 in the box that says FCC Registration Number. If you do not have your password, follow the instructions just below that box that says Forgot your password?
and click on the link that says Contact Tech Support. Yes, this part can take a couple of days, but once you have it, write it down somewhere.
Step 6) Once you actually get to the ULS Online Filing, you will see where you can click the option to renew, but only if you are within the 90 day window. If you license has already expired but it has been less than 2 years, you can still renew your license without having to take your tests all over again. But of course, you can not be on the air until your license renewal has been processed.