This is a good article to install mongodb step by step.
How-to-install-mongodb-on-ubuntu
Click here for mongoDB tutorials
To start the mongodb server: mongod
You may find an error that the database directory has not been created. For this
Create a database directory (default path): mkdir -p /data/db , and then start your server again. If you did not find an error, skip this part. You can also change the path to the database directory. Here is the command for this mongod --dbpath /your/path

Open a new terminal and run: mongo

If you have any questions, feel free to comment. Good luck.
Darshan patel
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