For the best experience, we recommend that you start off with Thunderbird Desktop or a Desktop browser like Firefox, Chrome, or Safari.

If you have Thunderbird Desktop installed, install the Thunderbird Pro add-on as per Install the Thunderbird Pro Add-on in Thunderbird Desktop. If you are not a Thunderbird Desktop user, please register at the link in the email we sent you.
Login. You'll have to enter a credit card number even though you may have a Thunderbird Pro coupon code (have problems with a code that you received? please ask for support). Currently, only credit cards are accepted. Apple Pay, Paypal and other 3rd party services are not currently supported.
Configure Thunderbird for Desktop for Thundermail as per the article Thunderbird for Desktop and Thundermail.
Configure Thunderbird for Android for Thundermail as per the article: Thundermail and Thunderbird for Android.
Configure Appointment as per our Appointment articles.
Configure Send as per our Send articles.

Go forth, set up some office hours with Appointment, send some files with Send and send and receive email with Thundermail!

Getting Started with Thunderbird Pro