1. SSH to your Ubuntu server
2. Import the v3.6 public key used by the package management system

   sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 2930ADAE8CAF5059EE73BB4B58712A2291FA4AD5

3. Create a list file for MongoDB v3.6

   echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.6 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-3.6.list

4. Reload local package database

   sudo apt-get update

5. Update to the latest stable version of MongoDB

   sudo apt-get install -y mongodb-org

6. Check the result

   mongod --version

   You should see "db version v3.6.0"
7. Enable backwards-incompatible 3.6 features
   Run the setFeatureCompatibilityVersion command against the admin database:

   db.adminCommand( { setFeatureCompatibilityVersion: "3.6" } )

Congratulations! You are now have MongoDB 3.6.0 installed on your Ubuntu server.