Follow below steps to install Using composer : 

- composer require --dev magento/magento-coding-standard
- php bin magento setup:upgrade
- php bin/magento cache:flush

You are done with installations.

Now, You can check Magento coding standard errors using the below command for Custom module :

vendor/bin/phpcs --standard=Magento2 app/code/Vendor/Module

After running the above command, you can see coding errors and warnings. You need to resolve those errors & warnings by adopting Magento coding standards.

That’s It.