When you create your Duplie instance, we will also create a volunteer application form.  You can view this form as an admin by logging in and going under forms and then selecting it from the list.  This form can be customized to collect whatever fields you need.  It's a good idea to put a link to this form on your website.  Once a volunteer submits this form, their account will be created.

Another option is to import users/volunteers into Duplie.  You can do this as an admin by going to Users and then Import Users.

After you have setup your events, there are a variety of pages to list your events in Duplie.  These are all public pages, so you can link to them from your website.  Events may or may not show depending on their privacy.  Here are some of the public pages to display your Duplie events.

https:// [your-instance] .duplie.com/EventCalendar.jsp

https:// [your-instance] .duplie.com/EventTiles.jsp

https:// [your-instance] .duplie.com/EventList.jsp

https:// [your-instance] .duplie.com/EventDashboard.jsp

If you want Duplie to "intake" new volunteers, we do have that ability using Forms.  We should have created a "Volunteer Application" form when your instance was created.  Modify that form's fields to meet your needs.  That form can be found under Forms and Manage.  

When trying to sign up, if the user does not have an account, they can click register on the login page which will create them an account.  If you have volunteer roles/shift that are private or protected, you will need to give new users access to those roles before they can be visible to the volunteer.  You can assign access by associating a role/shift to a group, and then adding your users to that group.