Rusty , you can coat it with 25/75 glue/water , varnish it , prime and paint , or just paint it , or you can just leave it like it is ... Whatever You want ... Just glue the inside on , just like you did the outside ...
Hint: .... as we’ve discussed many times before , it’s easier to apply the fabric to the inside and ceiling
before assembly , where the panel can be laid on a nice flat surface to work on , making things Much easier ...

Then glue the panels together as normal , and don’t worry, the glue to fabric joins are likely stronger than just foam to foam ... If you use enough glue ...