harmonize minor scales

Hi, I'm confuse. I want to harmonize Minor scale.But,there is the natural,harmonic,melodic.Please Can you explain to me how to harmonize them and do I have to harmonize each one different then other ones, And why just put at the key signature F#,D#,C#. instead of ad D#,C# next to the notes, Thank you

Usually, in the minor mode the key signature is the one of the natural scale. And if you use raised tones, you write the accidentals.

On the other hand, in tonal classical music, it's usual to take chords from one scale to another, mainly when yo want a V7 (with sensible, raised grade VII), but you can take chords from the three scales at any moment.

Each scales, due to raised VII (harmonic) or raised VI and VII (melodic) form different chords. This means that you can change chords of similar function as we do in major mode with modal interchange. In fact, this is also modal interchange, if you consider minor mode as a big mode made of three submodes (natural or eolian, harmonic, melodic).

Sorry it's in Spanish, but easy to understand.

Función tonal = Tonal function

Nota a evitar = Avoid notes

T = tonic function,  SD = subdominant,   D = dominant

The eolian Vm7 is considered SD by many people (because of b7).