First you will have to make sure that you have confirmation of the Shop owner that you are able to assume one or more customers.
Assume a customer in the shop
- You will have to login in the shop
- You will see an icon in the bottom right corner. An example of this icon is shown below
- When you click the icon a box will show up. Click on the link 'Switch Identity'
- A new window will open up where you will see the customers for which you are allowed to assume their identity
- Click on the login link, the system will return you to the shop and logs you in as that customer. You will still see the purple box in the right bottom.
- If you want to switch to another customer. You will have to click again on the 'Switch identity' link. There you can pick another customer.