Navigate to
Grand Theft Auto V\scripts\Superman V2 script files\Suits
Drag and drop suit_Superman_JL_DreadnotQbreak.ini into "Suits"
I recommend downloading JulioNIB's Quantum Break script and combining it with JulioNIB's Superman script if you want to experience Superman's movie accurate super speed!
Quantum Break mod: https://gtaxscripting.blogspot.com/2016/03/gta-v-quantum-break-script-mod.html 