Your Nexudus account has a sign-up form that can be accessed via the space website to register members/contacts. This form has several default fields, but you can add to them using Custom Fields. You can add a Custom Field via CRM > (Shortcuts) Custom Fields. Click the Add Custom Field button to add a new custom field.
On the next screen, fill in the fields needed to add the custom field and select if you want it to be a required field, by enabling the Make this field required option. Enable the Display in sign up form option if you want it to be displayed on the sign up form.
If you would like to carry out further customisations, don't forget that the web template code is available via Settings > Website > Templates > Open template files > signup.htm. If you'd like us to customise the form for you, please contact us at firstname.lastname@example.org and we'll examine the changes you'd like to make and offer you a quotation.