Bootstrap pkg on a disconnected system

I have an older laptop that I was playing around with, and installed
FreeBSD 13.2 from a previously burned DVD. I can't use `pkg add` to add
a package because `pkg` has not been bootstrapped. But the bootstrap
process insists on connecting to a remote repo.

I see the `pkg` package available on the DVD at
/packages/FreeBSD:13:amd64/All/pkg-1.19.1_1.pkg. If that can be used,
how do I bootstrap the pkg system first?

I can connect a USB interface, but am curious to know if this can be
done.

Thanks and regards,
Pat