One way to create an invoice is to go to the "Finances>Invoice" tab.

You will then click the "New Invoice" button.

You still start by selecting what customer this invoice will be for.
If you need to add a new customer, click the "+" button

Then start adding the items and services to the invoice.

You can also add a package of items and services to the invoice.

Next, you will see your "Terms" and "Notes Visible for Customer."

You can edit these areas at this time or in your settings.

(Note: If you change these areas while creating a new invoice, the changes will only apply to the current new invoice. If you want the change made to all future invoices, you will have to edit them in settings)

Once you are happy with the invoice, click the "Save Invoice" button.