The Requirements are MSVS and an Intel Compiler. The procedure can be found here: https://www.youtube.com/watch?v=T3hAV8gfnec. Shoutout to him.
First: Compilation of the cpp-file. You need MSVS to create an object-file in the MSVS Terminal. The Compilation Flags can be found in the win86_64 file from Abaqus. In my Example you also have to insert Eigen and its folder directionary.
Second: Execution. In the Abaqus Terminal with the Command: abaqus user=umat job=umat analysis interactive Visualization with abaqus cae database=umat.odb