The first step is definitely checking your gain staging. Regardless of what app or DAW you're using, your audio interface controls the volume of your mic going in to your computer. I'm sure you've done this, but make sure you're giving it enough gain to begin with. By default, the level in any app or DAW will be based on that. So, if you've got your gain turned up on your interface and you're still not getting a solid level, then that would indicate something faulty in your recording chain. (bad mic, bad cable, bad interface, etc.) There is no better answer. You wouldn't want to try to boost a low signal in post, because you'll be boosting a lot of noise along with it. You have to have an adequate, clean signal going in to start. Good luck to you!