将新项目添加到TFS中的现有解决方案

I added a project to an existing solution that is currently under source control using TFS, but for some reason I cannot check in the new project. When I view my pending changes, none of the files in the new project show up. None of the files have a plus (for a new file) next to them. What did I do wrong? How do I fix it? It's time to check in.I added a project to an existing solution that