I'd be happy to help clarify what my colleague meant when they said file menu. When you open up an invoice you'll see some icons for New, Save, Delete, Etc. It'll look like this:
From here you need to select the memorize option and a new pop up will show. Just fill in the information you want such as how often, next invoice date and what kind of reminder you want for it. Once done it'll save your invoice and either notify you or create it for you automatically. All you'll need to do is email or print the invoice out if you provide a copy to the client.
If you have any questions let us know and we'd be happy to help.