Open a console in Linux or a prepared command shell in Windows where abaqus can be executed. In Linux, enter

abaqus verify -all

For Windows it might be required to navigate to the Abaqus commands directory first. Then enter

abaqus.bat verify -all

Abaqus should start and run a couple of tests including checks if a Fortran compiler is linked.If no Fortran compiler is found or the tests are not working, please consult your Abaqus manual.