Open Sound Forge. Click "File," "Open Recent." Click on the song to be mastered. This opens the sound as a collection of multi-tracks.
Click "File," "Export as Wav." This converts the multi-tracks to a single .wav file.
Click "File," "Open New."Click "File" again and select "Import Audio." Select the exported .wav file to import it. This opens the .wav file as an individual track in Sound Forge.
Hit "Play" so you can assess the mastering process in real time.
Click "Tools," "Wave Hammer." This functions as a compressor. It limits the overall range of the dynamic and makes it louder, by cutting the very loud peaks and boosting the very quiet lows.
Adjust the "Threshold" slider dial. This determines the volume level at which cutting and boosting occurs. Set it to as high a level as possible before the audio begins to sound "fuzzy." Fuzziness is a sign of over-compression.
Adjust the "Ratio" slider. This dictates the degree to which the compressor adjusts the signal. A high ratio cuts all strong signals and boosts weaker ones. Set this dial lower. A high ratio can remove dynamic "personality"; if a singer's breath is boosted to the same level as her singing voice, it will make her sound robotic.
Increase the "Output Gain" slider dial. This determines the amount of "boost." Aim for as much "boost" as you can before fuzziness occurs. Once you're happy, click "Save As."
Click "Tools," "Paragaphic EQ." This boosts and cuts frequency ranges. When it opens, the audio is split into four bands. Adjust the "Ratio," "Threshold" and "Output Gain" dials using the basic compression principles applied to the "Wave Hammer" to improve weak frequencies and cut over-dominant frequencies. When you're happy with the mix, hit "Save As."