Hello,
You don't need to do anything to add it to LEAP. When you install NEMO it should "see" your GUROBI installation and automatically support it. LEAP will then detect which solvers NEMO is supporting. Note however that NEMO currently only supports Gurobi versions 9.0-9.1. See this page for more details: https://sei-international.github.io/NemoMod.jl/stable/faqs/#Installation