KSU-Chappell
Pawpaw in the US

Pawpaw seeds need a bit of special treatment, like a cold stratification period first, so do your homework on that. You'll want to sow them indoors, really, in individual pots about an inch deep, anytime from January in warmer zones right through to May in cooler spots, depending on your USDA zone. Check the GrowMore CookMore app, it'll give you the proper timing for your area, from February in zone 9 to April in zone 3. They need warmth to germinate, around 70-75°F, so a heat mat helps. It takes a fair while for them to get going, mind, so be patient.

Once your seedlings are a few inches tall, and all danger of the last frost has passed, you can start to harden them off. This means gradually getting them used to the outdoors over a week or two, you know, a bit like easing yourself into a cold bath. Plant them out in a sunny spot, or partial shade when young, about 15 to 20 feet apart, as they grow into decent-sized trees. They don't really do well in containers for the long haul, to be honest.