To change the currency of a company, follow these steps:

1- Select which company you want to change the currency of. You can quickly access your list of companies by clicking on the ARROW next to your company name (near top-left).
For more information on how to access your list of companies, consult the following article:
How to access my list of companies

2- Next, click on the "Company Settings" button in the TOP MENU.

3- Once in the edit menu, select a currency from the drop-down choices in the field “Currency and save your choice.

Related Articles (Please refer to the links below)

- How to change the name of a company?

- How to change my company's country/province/state?

How to change the year-end (end of the fiscal year) of a company?