First, click Options -> Analysis options, then select the ‘categories’ area. Here you can see all categories and, when one is selected, the other settings that have been configured (including the keywords, whether the category is output as a separate tab in Excel, and also whether the transactions matching the keywords are restricted to receipts/payments/both). Additionally, you can set the order of priority incase more than one category matches against a single transaction, by moving categories up and down in the list shown, and also, you can select if the keywords should be identified as separate words (for example, if this option is selected this would disallow a match for ‘fee’ in ‘coffee’).
For example, for a new ‘HMRC’ category, enter a new category title (e.g. ‘HMRC’), click to add the category, then add the category keywords (e.g. ‘hmrc,hm revenue,vat’) and select the other settings. Finally, save the options.