I use mine diluted according to the directions on the bottle in a spray bottle.
If you want to do an allover starch job, wash the fabric with a color catcher, rinse and spin as usual, then soak the fabric in a diluted starch mixture - either in a bucket or the washer, spin and dry. Do not rinse the starch out. I think that's how my mother used it. I can remember dipping just the skirts of my little girls' dresses in a bowl of starch. I didn't want to starch the bodice and the seams that touched their skin. That was a long time ago.