transmission issues

I just had a friend help install a partially rebuilt y1 transmission in my 93 gs along with a new exedy clutch complete kit and flywheel and for whatever reason if I immediately clutch in and shift into first at a stop it will grind, as well as I cannot downshift into second without revmatching. I have no idea if the thing needs to break in or clutch adjusted or what. They guy that rebuilt it is pretty well known in my area for quality work. other than this itll shift fine every other gear.