Can someone help me with the choise of student dormitory in Compiegne? 
For this kind of housing you have two choices.
The first one is the CROUS: (The regional affiliates of the French national student service agency). They are in charge of the public university residences. Compiègne has 3 options:
- Roberval (close to BF)
- Du Parc (close to PG)
- Peuplier (close to PG)
That’s where generally, international students choose to live, because the rooms/kitchens are fully equipped with furniture, and the rents are not so expensive (from 250 to 400€ all charges included).
Which location is better?
BF means Benjamin Franklin, it's the name of the main building of the University located in the city-center. Most of the course are taking place there, but it depends of your department.
PG means Pierre Guillaumat, it's the name of the other building located 15 min by bus (ligne 5, it's free) from the city-center. It is composed of 2 buildings : PG1 and PG2. It's also close the Research Center (Centre de Recherche : CR) and 5 min from the Innovation Center and the Sport Hall.
If you study GSU (Urban System Engineering), Design, Innovation, you will have part of your courses in PG.
The associative life of UTC is mainly located in BF.
Is there any Fb group or website for Erasmus students?
Yes there is a FB group to exchanges information about housing or finding flatmates :
What are the other options ?
The second choice is the ALESC(Organization for the housing of Compiegne’s Students and interns).
This organization possesses 3 residences (La Ruche and Danielle Pommery close to BF and La Mare-Gaudry between BF and PG).
The recidences have been recently renovated, and in la Mare Gaudray as well as in Danielle Pommery have the possibility to have flatmates ( sharing the kitchen and the bathroom with one or two students). 
The ALESC also makes it easier to contact people renting their flat to students. You need to pay a 26€ fee, and you are able to access the renter’s contact, except if you are allready student in Compiègne.