Yes you're right, in this case it is incompressible laminar flow that is computed with OpenFOAM. So to use a turbulence model you would just have to select the corresponding model in the OpenFOAM settings dialog box (not the Navier-Stokes physics settings dialog box). Similar to "step 16" in the Pitz and Daily turbulent flow over a backwards facing step tutorial
https://featool.com/model-showcase/04_Fluid_Dynamics_08_turbulent_flow1and then use this turbulent flow field as in the previously linked tutorial.