If you don't have an existing user, you can sign up as a new user on the Spacent app. If you're a company user, use your work email to be connected to your company's membership.
Start by downloading the Spacent app from App Store or Google Play Store. After downloading the app, it will ask you the email you wish to use the service with.
After submitting your email address, a verification code will be sent to it to verify that it's really you.
Next the sign-in flow will take you through choosing your region, accepting the User Terms and adding a name and a phone number to your account. The last steps may be skipped for now, but you can't start making reservations without them.
If you're an individual user, you can get started with a Free Plan that allows pay-per-use bookings, or you can request a trial of a Business Monthly Plan, which allows unlimited amount of hot desk reservations per month for a fixed price.
And just like that, you're ready to start making reservations! You can find instructions on how to make reservations here.