The easiest way to install docker with installation script. Below is the script url. Make sure the user should have sudo privileges.

https://get.docker.com/

Execute the below two commands to install docker.

$ curl -fsSL get.docker.com -o get-docker.sh
$ sh get-docker.sh

[centos@docker-server ~]$ curl -fsSL get.docker.com -o get-docker.sh

[centos@docker-server ~]$ sh get-docker.sh
# Executing docker install script, commit: fc04d2c
+ sudo -E sh -c 'yum install -y -q yum-utils'
Package yum-utils-1.1.31-42.el7.noarch already installed and latest version
+ sudo -E sh -c 'yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo'
Loaded plugins: fastestmirror
adding repo from: https://download.docker.com/linux/centos/docker-ce.repo
grabbing file https://download.docker.com/linux/centos/docker-ce.repo to /etc/yum.repos.d/docker-ce.repo
repo saved to /etc/yum.repos.d/docker-ce.repo
+ '[' edge '!=' stable ']'
+ sudo -E sh -c 'yum-config-manager --enable docker-ce-edge'
Loaded plugins: fastestmirror
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After completed, execute below command to run docker commands as non root.

sudo usermod -aG docker your-username

[centos@docker-server ~]$ sudo usermod -aG docker centos

Start docker 

[centos@docker-server ~]$ sudo systemctl start docker 

Check version of Docker

[centos@docker-server ~]$ docker --version 
Docker version 18.02.0-ce, build fc4de44
[centos@docker-server ~]$ 

To uninstall docker, execute below command

[centos@docker-server ~]$ sudo yum remove docker-ce