All the types of substitution you learnt in major keys (relative substitutions, scale tone triads or 7ths two degrees ahead in the key, dominant minor, and tritone substitutions) can be applied to minor keys as well.
The main difference you will find is that when you start to go into the upper extensions of chords built on the harmonic and melodic minors, you will get alterations to the chords. Shown below are the chords resulting from substituting scale tone 7th chords two ahead for the standard scale tone 7ths of A melodic minor.
Here is a solo based on the progression to"Black Orpheus" by Louis Bonfa. It is in the key of B minor and makes use of some of the new chords you have learnt. It also contains a section in D major which is the relative of B minor. Learn the solo, analyze it and then transpose it to all twelve keys.