How can I create two separate quicken accounts?

Jeffsqkn

Example: I was handling someone else's finances

Greg_the_Geek

Just create a new Quicken data file. File --> New

jacobs

Just a note about terminology: you asked about having two different accounts, but it sounds like what you want is two separate data files. An account in Quicken is each bank account, credit card, brokerages account, loan, etc. that you see in the left sidebar of the Quicken window. But if you're doing record-keeping for a different entity, such as a parent, child, non-profit association, etc., you want to have two separate data files, each with their own accounts, payees, reports, etc. 

You can have as many separate Quicken data files as you wish, and there is no interaction between them. And as Greg said above, it's as simple as using File > New to create a separate file. If you have two files, you will easily be able to switch between them using File > Open Recent, where the top two items in the pop-up list of files will be your two most-recently opened data files.