R/S Absolute configuration: how to decide if it is R or S configuration ?if it given that (1) NH2 will be in the position of W (2) CH3 will be X (3) Cl will be Y (4) CH2NH2 will be in the position of Z I will attach a pic to show the place of compounds

The configuration is (R) .

Let us write the structure of your molecule first and assign priorities:

Priorities are assigned based on the atomic number. The rule is the following: Assign priorities (1, 2, 3, or 4) to the atoms directly bonded to the stereogenic center in order of decreasing atomic number.

Next we look at the lowest priority substituent (##CH_3##), it should be facing backward; which is not in this case!

The rule is very simple, you switch places between the lowest priority substituent (##CH_3##) and the actual substituent facing backward (##CH_2NH_2##), here is what you get:

Label the new configuration after rotation; it is going to be (S) . Flip the configuration: Which means since it is (S) it will become (R).

You’re DONE.

Note: some textbooks mention that you have to rotate the molecule, which means you have to work your imagination, since it is a 3D molecule and you are working on a 2D surface (the paper or computer monitor) sometimes it becomes confusing, this method is way simplier.

Here is a video on labeling stereogenic centres R and S. There is part 1 and part 2.