It depends what you mean by "share". If you just mean to "distribute" it, then that's just a matter of compiling your program in release mode (after being completely finished with it), packaging it in an installer, and distributing it (for free or for cash). If you mean sharing code with others (in the hopes that they will contribute to it), then you need to get them to sign an agreement (physically sign a paper, anything else is worthless) on the terms of their involvement, which can range from relinquishing all their copyrights to you, to giving you license to use their contributed code under specific clauses (e.g., it can be free of charge but closed source, or with a royalty, etc.). And, it goes without saying that if you are using code under a copyleft license (like GPL) then you don't have much choice, you must distribute your game as open-source, under the same license.
As for distribution (within an installer), then it is just a matter of picking one of the hundreds of sites that host freeware / shareware programs for download. Of course, you probably should first test that your program installs and works on many platforms (especially if in Windows). You can do that by asking friends or family that can give you access to a few different Windows computers with different versions and without any developer's libraries installed (like Visual Studio or whatever else), this is important to make sure you don't have dependencies. And I think Visual Studio or other build systems should provide tools to allow you to distribute your game easily (i.e., package the installer and resolving dependencies).