How to group data with matching categories?

Hi,

I'm new to PowerBI and I'm experiencing a problem when I am doing my report.

1. In my data, I have "customer" column(description) and "sales" column(number),  I would like to make a group of some certain customers with their matching sales. Tried many ways but does not work. 

2. After making a group of customers, I would like to calculate their percentage of all cutomers sales. 

Could someone help me with my questions, please?

Thank you!