I need an introduction to MongoDB/NoSQL Database [closed]
You could start here.
How do I build my models, how do I add relations between different "tables"?
A non-relational approach is the best path to database solutions which scale horizontally to > many machines.
MongoDB stores data in JSON documents (which we serialize to BSON). JSON provides us a rich data model that seamlessly maps to native programming language types, and since its schema-less, makes it much easier to evolve your data model than with a system with enforced schemas such as a RDBMS.
Check also What is NoSQL, how does it work, and what benefits does it provide?, I need an advice about NoSQL/MongoDb and data/models structure and Converting simple MySQL database to a NoSQL solution