Sure, go ahead and put on the flaps. Your radio can probably handle them. If not, it won't matter, because at the rate you are going, the plane may not last long. Sorry for being harsh, but very many of the warbirds that are built by people who have never flown either end up not flying at all, or have a very short life span.

The reasons for this are as follows. Warbird kits are not designed for first time builders. The instructions assume the builder knows what he's doing. Consequently, the first time builder makes many mistakes. These include things like too much glue, but not in the right places, making the plane heavy and weak. They also include warped and misaligned flying surfaces, poorly done control rods, and a host of other problems. Assuming the beginning builder actually manages to build a decent plane the next issue is flying it. Sometimes he heeds the voices of experience and hangs the plane up while he goes off and seeks some time on a trainer. Unfortunately, running through his mind is that cool warbird he's got hanging up. Often, rather than getting in enough time on the trainer and then gradually progressing through several other planes to build the skills needed to ensure success with a warbird, the urge gives in and he decides that since he's soloed on the trainer, he's ready for anything. Net result, scratch one warbird.

So, my advice would be to immediately stop construction on the warbird. Get yourself a good ARF trainer and use your radio and engine in it. While you're learning to fly the ARF, build yourself a good second plane from kit. There's lots of recommendations in here. Once you've graduated to the second plane, begin building your third, or if you are doing really well, perhaps begin work on your warbird again.

This is my advice, do with it as you please.