To change the currency of the estimated value of the opportunity you need to open the opportunity list.
Step 1: Open the opportunity list
Open the opportunity list and switch to the grid view.

The grid view
Step 2: Click on the heading of the value column
Click on the heading of the value column and choose the edit field option from the list.

Choose edit field from the list
Step 3: Choose the currency from the list
Choose the currency from the list and click save.

Choose the currency
Notice: Our system only change the symbol of the currency next to the estimated value, but do not take into consideration the conversions of currencies.