Mongo Db schema

Mongo Db schema

I have to save the different profiles of a user from various social
media.for example user may have 1 facebook and 2 twitter profile. if i
save the each profile it is inserted as a new document and how would i
relate this document to another. I used dot notation in mongodb. if i
relate the facebook and twitter profile of a same user means it is easy to
fetch the record.How would i design the schema ? and also how would i
avoid duplication? Is any possible to use the facebook id twitter id as
unique? I am new to mongoDB.