I don't know if anyone mentioned this...but that is a pretty small space for that number of birds. They may seem
small right now but soon you will have some overcrowding issues.
Other than chasing them in each evening, or offering a scratch snack in the coop at dusk and shutting them in, I...
Keep them locked in the coop for a couple of days and even up to one week. They will get used to sleeping there rather than the run and will actually prefer the safety of the shelter. Especially if they discover the roosts.
You can even turn on your light at dusk and they should gravitate...