Yeh basically having music based in G minor means that the music links closely to the note G...
Note B and E are both flattened so everytime you play a B or an E, you need to press the black key before it instead, Those black keys are called Bb (B flat) and Eb (E flat).
If you play the chord G + Bb+ D, which is the G minor chord... this chord should always feel like 'home' within the piece of music you are making because it is the root chord (The first chord of the G minor scale).
I tried explaining this the best I could without going to deep in to music theory. Just in case you don't know much music theory, it does help to maybe check a couple videos out on music theory on youtube which are aimed at producers, if you look for these videos, find the ones that talk about scales, harmony and melody.