You need to do some research and find the exact pinout of the 3.5mm mic input on your radio. The standard 3.5mm stereo jack on your computer has a left, right, and ground pin and may not be in the locations your radio needs.
Once you know the pinout, you can cut off the pin on a cable and solder a radioshack one on connecting it according to your radio pinout. You may need to buy a mono (one channel) audio cable to do this instead of a stereo cable.
Yaesu VX-7R, Vertex VX-414, Alinco DR-140TQ, Yaesu FT-897