And I need to know how to make one instrument follow a 3/4 time signature while another is in 4/4 time signature for the same bars.
Thank You
i dont think you can but if the instruments end up playing the same thing at some point then just keep it as 4/4 so the other instrument will be like

ends up lining up in some form sooner or later.
yeah you cant, i have spent time trying to do it and cant find out how, i guess you cant. you will just have to do the math.
The following solution will provide playback identical to 3/4 against 4/4 without you needing any math. However, the standard notation score will not read as 3/4 track but rather as triplets of double note value. Happily this discrepency won't show up in the associated tab score.

Set the basic pulse of the track that is required to sound as a 3/4 part to 3 minim triplets. The program will automatically calculate any further subdivisions you require. Also you will need to double the note values of all the notes you place in this part.
That is, where you normally use a crotchet in 3/4 it will be a minim (triplet), a quaver will become a crochet (triplet).