Let me give you a quick tour of the platform.

How to Change Product Currency

To add a purchase option inside your form, click Advance element.

Click on Advanced

Drag and drop Purchase element inside the form builder

To add or choose to product, clik on this drop down button and choose "Sell Products"

Choose Sell Products 

Click on Products

As you can see on thois area it will only show the products created using USD currency, if you can't find the product you want to add here it is because you are using different currency AUD for example.

Click on Create/Select Product

Let's change the Currency setting first by clicking the setting button

Click on Settings

Choose the currency of the product you created and you want to use on this purchase form.

Click Currency drop down button

Click on Ok

Click on Save

Click on the settings icon

Click on Create/select button

The form only let you choose one Currency, so make sure to change the curremcy setting if you are using different product currency.