Plug the phone into the computer. You should see the phone in the computer as a new device or disk drive. Open it to the place you want to put the file. Drag it from the computer to the phone. After it copies, do a safe remove of the phone. (Windows doesn't always finish writing when the copy claims it's finished, and disconnecting the phone before the write is finished will corrupt the file - that's what safe removal is for, it's a "finish writing NOW!" command to the computer.)