I just want to know how to use the model loader block.

Do you mean the entity manipulator or the image loader? I am not sure how the image loader works, but this is for the entity manipulator:

Right click on the dalek and a GUI should appear.

Top left, there should be a box that says 'thedalekmod:dalek'. This is what you need to change.

Delete the word dalek so that you are left with 'thedalekmod:'

Finally, you need to put in the name of the mob you are trying to show. For example, thedalekmod:cyberman for the 80's cyberman.

If you need the id for anyother mobs, check the website for any forums or ask on the discord. I am sure someone would be able to tell you.

Hope this helps.

-DT10