It's a little work the first time, but here's how to get your 2015 transcript (with AGI) from the IRS website:
1) Go to www.irs.gov/transcript
2) Select the Get Transcript Online button (you may be prompted for an authentication process)
3) Choose Federal Taxes as the reason
4) In the Record of Account Transcript section, click on 2015 (see screenshot)
5) When you open the transcript, scroll down to the bottom of the Adjustments to Income section
6) Your AGI is the last number in that section
Hope this helps.