Answer:
:
First step while writing the R - S nomenclature is to identify the atoms and their atomic number.
Here we have - H - 1
F - 9
Cl - 17
Br - 35
Now, we need to place the order of priority accordingly. So, the order of priority would be
Br > Cl > F > H
Now, we need to place the atom with the lowest priority at the back, i.e., facing away from you when you look at the carbon. Let’s do that now.

Here we have H above the plane and F below the plane.
If I need H to be away, I need to look at this molecule in this way.

I hope you can visualize this.
Let’s draw this like this and number it.

Another way is to convert this to Fischer projection. You will learn that soon.