Please create the necessary fluid domain from your solid geometry. Depending on the Reynolds number of your problem, please use the appropriate Viscous model (laminar or turbulent). Please make sure to use the following boundary conditions in Fluent.
1. Inlet - Velocity Inlet,
2. Outlet (all your small perforations) - Pressure Outlet
3. Rest of the boundaries (incl. the other end of your pipe) - Wall
Please see the following videos to understand the workflow from geometry to meshing to set-up to results.
In addition to this, there are numerous videos on YouTube (on the Ansys How To channel) that elaborate on the problem set-up.
I hope this helps you get started.