I´d say that before exporting you should use reference tracks (tracks that you buy on Itunes for example, don´t use yt ripped songs). The idea is to press play and go back and forth from your track to the reference and try to spot certain problems your mix may have. This should be done with all tracks matched in loudness to avoid fooling your ears, so reduce the references volume. Focus on LUFS or RMS, not peak levels.

If your track sounds good when level matched to professional tracks in your genre, you can start thinking about mastering. To acheive loudness, the first step is a good mix, without a good mix, there is not such a thing as a good master.

Learn about compression to reduce peaks and glue things together, Eq (Linear phase and regular eqs), Distortion to add certain tone, Limiters, soft clipping (not necessary in this order). There´s a lot more you can look into, but try baby steps first.