Positioning your subwoofer can often be a shit fight, with the correct locations being different in every room.
A certain amount of playing around is going to be needed to find that sweet spot in your room. The main requirement is that the location of the subwoofer not be audibly apparent.
One technique that can be used to find an optimal position is to place the sub near the listening position, and play a track you know very well with plenty of low-frequency content. Then, move around the room listening at likely subwoofer locations and choose a spot that delivers the smoothest bass response. I’ve found crawling round the room works best, but you might find just staying standing in enough. The spot where it sounds the best is where you place the sub.
With most home studios, the room that is used is normally of symmetrical design. This makes it very tempting to just plonk your sub inbetween your speakers, or right next to your desk.
However, this is only going to cause an uneven room response as these postions often create symmetrical standing waves. Placing the sub slightly asymmetrically will often give much better results.