I started CFD in OpenFOAM with no prior experience in CFD. I did not even have the Navier-Stokes equations memorized or anything. Do not write it off as impossible without even trying, as I had.
A quick and useful introduction to CFD in general is available here.
Once you have some grasp of what CFD is about, you can move onto installing and using CFD programs. A great resource for all steps of the whole simulation process is CFD-online. This website was essential for enabling me to run my own simulations.
I would love to elaborate on whatever you cannot find in the two resources I described above. Please comment if you have any questions at all, and I will be sure to reply in a short time.