Commerce Point of Sale (POS)
You will find some documentation in the README.txt that comes with the module.

To use the module, you first need to get drupal commerce up and running. Then your products will be available for sale via the POS, once installed.

Also look at the commerce pos issues queue as v2 still has some issues being resolved.

I have used 7.x-1.x-dev extensively, and you can access the POS via: admin/commerce/pos

The configuration is via: admin/commerce/pos/config

If you have any specific question, please amend your original question.

Edit:


Make sure you are using the latest 7.x-2.x-dev version to get latest fixes. 
Also see this issue relating to products not showing: By default, no products are available in the POS
POS is available via: admin/commerce/pos