If you select 'Suppliers' from the top left, and then 'Manage Purchase/Nominal Accs' from the Purchase Orders menu, you can search for, view and create a Purchases Account.
To view or edit a Purchases Account, click 'View' beside the account, which opens a new page where you can view and edit account details.
To create a new Purchases account, first click 'Create Account' (below the search field). Then you can provide the Purchases Account Reference and Name, and assign the account to an existing Nominal Account from the drop-down menu, or assign it to a new nominal account. To assign to a new nominal account you must provide the Nominal Account Reference and an Account Description.