I copy and pasted their abilities in here just in case you didnt read in the pdf. These are their general abilities but they can do many more things like charge your chakras, clear your aura or environment and even influence events. You have to first establish clear communication with them first because they will not understand you first. So you need to tell them what you want them to do, such as charge your heart chakra by saying it verbally and it really helps to also vizualize your heart chakra being charged and feel it as well.

That would be much easier for the servitor to understand rather than you just saying it. Teach it the sigils that come in the book for jing, shen, chi energy and tell them to engorge you with that energy in a certain place in your body. Although you might not be energy sensitive or feel their feedback, they will begin to understand you and and work on what you told them to do to the best of their ability and depending on how well they understood you.

And if you want to feel their feedback, be really aware when communicating with them and notice the subtle changes that occur when communicating with them. Its harder to catch when youre in a beta brainwave state but much easier to catch in a relaxed, meditative, deep brainwave state like alpha.

Dark Servitor
It will be able to use a wide range of psychic combat abilities, would be able to
create minor energy realms (for your own uses, energy storage etc) It would be
able to protect you from lesser malicious entities. It would be able to cast spells
on your behalf, can cast a wide range of darker magic forms including the Goetia
along with the summoning and control of Demons (goetia type).
There are lots of other abilities that you can discover on your own through your
own experimentations.
Light Servitor
This one has some combat abilities as well and a large number of shielding
abilities, this servitor has some healing abilities which it can use on you or other, it
would be able to cast spells for you as well but only of light oriented types, and in
the same vein as the dark natured servitor way it would be able to summon light
and angelic type entities.
As with the dark natured servitor there are a host of other abilities you can
discover on your own through your own experimentations.