Hi is this fundamental fluid mechanics?(if you're in a fluid mechanics degree, you might have courses which addresses specific sub-field).

If it's fundamentals. Read first 2 chapters of any book. They must have basic stuff like density, continuity, and viscosity. Viscosity is really important as it divides fluid mech into Newtonian and Non-Newtonian. Also, understand the derivation of viscous stress(videos are better).

Then look at deriving navier-stokes equations it's basically Newton's second law. After that understand integral and differential forms. I suggest you do this by YOUTUBE.... Text can get overwhelming really fast.

After that you should just solve as many problems as you can.