A simple way to do this is to use the systemctl command:
$ sudo systemctl start docker
To check if your docker engine was started or not you can use this command:
$ sudo systemctl status docker
or you can also make use of the service command:
$ sudo service docker start
and check if its started or not using this command:
$ sudo service docker status
Hope that helped :)
Okay, if you are new to docker and need help in it try out docker training course.