Hi,
You don't give details. We don't know where you are now, what knowledge you have....
Start with doing internet search.
Mongodb is well documented, there are more than plenty informations in the internet.
When you do a search for "mongodb basic tutorial" or "how to start with mongodb"... there will be thousands of hits. From simple Internet pages, examples, even video tutorials.
Go through a couple of them and learn how to use mongodb.
A forum can't replace internet search, reading documents...
Klaus