The process for using the club website system depends on the event. Check the event description.
Interest in weekly events is managed by the individual trip leaders. You must contact the trip leader directly to be added to weekly event notifications.
Other events use a website registration system.
To be able to register via the website you must
a) be logged in to the website under the name or user id you want to register for,
b) have a current membership or financial subscription.
To see if your membership is current, when logged in, go to Your Club Memberships. Most memberships expire on the 31st of December each year. You can click on the expired membership to Renew or renew in advance.