How to create new table and copy column from another table

I have 2 fact table and both have customerId common. I would like to make relatioship with these 2 tables so that I can create common slicers in table. I suppose I need to create Dimention table for this.

But how to copy CustomerId column data from SalesFact table?

Obviously I first create new Table and rename it as DimCustomer. But cannot make correct formula to copy SalesFact.CustomerId data there.