Did your GM-15 come with a USB programming cable? If so, do you have a computer with Windows XP or later?
Which repeater only 3 miles away are you trying to reach: The Evanston 725 or the Lincolnwood 575?
Using my Baofeng UV-13Pro, which is the Ham Radio version of their GM-15, I would program Evanston 725 from the keyboard, this way:
Go to Channel 30, which is the preprogrammed channel for the 725 repeater;
Then push the MENU button and press the UP arrow key until you get to Menu #13 - Tx CTCSS and then press Menu Again and either "OFF" or a tone number, such as "67.0" will appear and use the UP and DOWN arrow keys to get to "100.0" and then press MENU again to confirm and store 100.0 into channel 30. Now press EXIT.
Now try to transmit to the repeater again and see if you hear the "tail" of the repeater after you "kerchunk" the Push-To-Talk button. Try it outside and even take a ride to the location of the repeater and try again. Identify yourself with your callsign and ask if anyone can hear you.
Good luck and report back!
Now to go back to sleep!
Be sure to stop at SuperDawg on the way home!