There is a checkbox in your Company Settings on the General tab where you are able to enable/disable expenses.  Existing users have expenses disabled by default so you will need to enable the feature, but new users have it enabled by default.

If you are setting up your Staff Squared account for the first time you can add your Office expenses settings when you complete your Company Profile. 

If you already have an account and want to set up expenses for your company, then you need to firstly go to your Company Settings, click on the More tab and then Expenses. 

This will take you to a new page where you will see a list of your existing offices.  To set up expenses just click on Edit next to the office name

and you will see a new page where you can complete the expense details for that office then click on Save

Or, if you want to set up completely new expenses for a particular office, then just click on Custom and add the new details then click on Save

Once all of your offices have been added they will appear in a list which you can edit by clicking on the Edit link.