If you are trying to harmonize the ........
1 degree of the scale try I, IV, vi or ii7 chords of that key, as they will have the 1st degree note in their makeup.
2 degree of the scale try V, ii7, iii7 chords of that key.
3 degree of the scale try I, vi, iii chords of that key.
4 degree of the scale try IV, ii, v7 chords of that key.
5 degree of the scale try V, I, iii chords of that key.
6 degree of the scale try IV, ii, vi chords of that key.
7 degree of the scale try V7, iii, Imaj7 chords of that key.