If this is on the same computer then you do not have to remove the license as the products use the same license.
It also is not necessary that you uninstall Visual Studio 2013 prior to installing Visual Studio 2015 as they can coexist. (unless you will not be using it)
1. Un-install VC 2.3 for VS 2013 Hotfix #1.
2. Un-install VC 2.3 for VS 2013.
3. Install VS 2015.
4. Install VC 2.3 for VS 2015.
5. Install VC 2.3 for VS 2015 Hotfix #1.