It's very simple to import a .bson file:
mongorestore -d db_name -c collection_name /path/file.bson
Incase only for a single collection.Try this:
mongorestore --drop -d db_name -c collection_name /path/file.bson
For restoring the complete folder exported by mongodump
:
mongorestore -d db_name /path/
Note: If you have enabled authentication use the below syntax:
mongorestore -u username --authenticationDatabase admin -d db_name -c collection_name /path/file.bson