Turn On Multiple Currencies Without Contacting Support
It’s now possible to enable multiple currencies instantaneously without contacting Salesforce Customer Support, or locking your org. These changes apply to Lightning Experience, Salesforce Classic, and all versions of the Salesforce1 mobile app.
To enable this feature, from Setup enter Company Information in the Quick Find box. Then select Company Information and click Edit. Enable Activate Multiple Currencies, and save your changes.