Right key your project in "solution manager(解决方案资源管理器)", choose the "Property(属性)" option.
Then select "VC++ Directionary(VC++ 目录)", and do the following things:
1.Add the path of sdl2's include folder to including directionay(包含目录);
2.Add the path of sdl2's library folder to library directionay(库目录);
3.Add the path of sdl2's binary dll folder to Windows Runtime directionary(Windows运行库目录).
At Last, Select the Linker->Input,
Add SDL2.lib, SDL2_image.lib and so on to Append Rely Objects(附加依赖项).
Attention:
Apply the settings to Release mode(and other modes) also, not only the Debug mode.