The 32-bit files are in i686-w64-mingw32
The 64-bit files are in x86_64-w64-mingw32

To install SDL for 32-bit x86 executables (i686):
    make install-i686

To install SDL for 64-bit x86 executables (x86_64):
    make install-x86_64

To install both:
    make install-all

Use DESTDIR to change the target location
    mkdir $HOME/mingw32-prefix
    make install-i686 DESTDIR=$HOME/mingw32-prefix

Look at the example programs in ./test, and check out online documentation:
    https://wiki.libsdl.org/SDL3/FrontPage

Join the SDL discourse server if you want to join the community:
    https://discourse.libsdl.org/

That's it!
Sam Lantinga <slouken@libsdl.org>