Just to give you an example. Play a simple melody on C major scale. Say, C D E C E. Now shift the entire melody by 2 or 4 notes. So that the melody starts on 3rd or 5th note of C major scale. This melody will be E F G E G in the first case. Now record the 2 melodies individually and then play them together. So basically its playing 2 solos at the same time. You have to find the supporting solo to the main one. For starting off, you can shift the main melody to the 3rd or 5th of the main scale. Shifting it to the 6th or 7th also gives an interesting combination. Or you can shift the entire melody up/down an octave as Steve vai has done in Tender Surrender. Take a look at the riff of Second Heartbeat. Whatever I said is not enough. Wait for advice from other people and also for yourself to try your hand at making harmonising solos.