You may hold assets and liabilities in multiple currencies around the world, but in order to get an aggregated view of your net worth you need to set your base currency.  This is the currency which will then be used for all reports and visualisations in vaultbox.

To set your base currency, click the Settings cog on the left of the screen, then select Exchange rates:

Click the edit button next to your Base Currency:

The following page would load:  

Type the currency you want, then click Save.