Signed-in users can also find this guide, with screenshots, under Help in the app.
Permit emails include a personal link to your permit. You don't need to sign in to use it.
When a space is offered, open the email and select the link. Select Accept the space before the date shown.
For card permits, each month you get an email a week before the month starts. Open the link and select Pay by card.
After paying you return to your permit page, which shows each month as Paid.