When you start the WinMain you define an integer, specifically int iCmdShow. You can call it different things but you can use that variable to show your window also. If you just want it visible that's how I do it, if I want it transparent or whatever I use those SW values. The iCmdShow integer is defined like this, in case you don't know what variable I am talking about.
Then just use the ShowWindow function like this:
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCe hPrevInstance,PSTR szCmdLine,int iCmdShow)
Note: Depending on the purpose of your program you may or may not want to include UpdateWindow. Usually you do but just in case you might not.