To configure MongoDB follow the steps below:

Start MongoDB using the command

sudo service mongod start

To verify if it is started use the following command

sudo systemctl status mongod

Output
mongod.service - MongoDB Database Server
   Loaded: loaded (/lib/systemd/system/mongod.service; disabled; vendor preset: 
   Active: active (running) since Fri 2019-07-19 16:50:52 IST; 15min ago
     Docs: https://docs.mongodb.org/manual
 Main PID: 30977 (mongod)
   CGroup: /system.slice/mongod.service
           └─30977 /usr/bin/mongod --config /etc/mongod.conf

Now stop MongoDB using this command:

sudo service mongod stop

Restart using this command:

sudo service mongod restart

Now, you can start using MongoDB.