I've never used Mixcraft but I checked the Mixcraft manual and it is likely to be something along these lines.

Click on the small keyboard icon at the left hand end of the MIDI track and then assign an existing preset to the VSTi, like this:

Attached Files (Click to download or enlarge) (Only available when you are logged in)
2020-11-15_16-37-04.jpg (25.06 KB, 58 downloads)
2020-11-15_16-30-54.jpg (180.29 KB, 57 downloads)

BIAB & RB2026 Win.(Audiophile), Windows 10 Pro & Windows 11, Cakewalk Bandlab, Izotope Prod.Bundle, Roland RD-1000, Synthogy Ivory, Session Keys Grand S & Electric R, Kontakt, Focusrite 18i20, KetronSD2, NS40M, Pioneer Active Monitors.