Yeah, you'll need to enter them manually. I can tell you, however, that there are some things you are likely out of range for, even with a Scantenna. I would stick with the TRACON lists, Andrews AFB, and in a separate bank for when the Prez flies to Camp David, the Guard Dog frequencies, along with the common 260.9 and 228.9 Huntress frequencies.
The Sticky Thread for Milcom in the Maryland forum would probably be a better bet to get some guidance as to what could be heard in your neck of the woods. But those would be good, pretty much for sure - heck, you might even turn up someone who has a .p97 file you can import
73 Mike