In the SAF, they are free to post you wherever needs manpower.
Sometimes it can be due to your civilian job experience or relevant
studies/qualifications.
Basically ESG prepares the logistics - such as equipment,
facilities and movement ahead of a unit or the SAF's exercises.
Units bring some of their own stores, but the bulk of things like
accomodation, sometimes weapons, etc. are provided by ESG for
better efficiency.
There's nothing much to prepare yourself for your role there,
I'm guessing you will be in-charge of some areas of logistics.
Since you're a 3SG, perhaps OIC for armskote or something...
not tough, just be meticulous, count your things, double-count
correctly, take care of your things not to be stolen, lock up your
stores.... Make sure people return things in good order, if
spoil/lost - make sure your procedures are right, else you sign
1206.
They will train you, give you all the info, guide you on what to
do there.
Don't worry...