Boosting the low frequencies with an EQ (or the opposite, old school method, cut highs, boost overall level.. traditionally better for analog) Another option is a multi-band compressor, which can be similar to the EQ method. Disable compression and use the multi-band output volume faders.. the compressor gain reduction functions can also be used (or abused)

A bass synthesizer process is another option, for instance the Waves Audio plug-in 'Renesounce Bass' (R-bass), however bass synth plug-ins are easy to abuse.. therefor I usually do not recommenced them for non-audio folks..

All said, it is best to record a great sounding track from the get-go, if not, it's just polishing a turd;