To create a ticket within your system use the Add Ticket button at the top of every page. 

If you have more than one Ticket Type, you will be asked which one you want to use. If you only have a single Ticket Type it will skip this step.

Ticket Hub Customer View

The form is based on the options you have set within the Ticket Type. The Title and Description box will always appear, but the other fields that are shown depend on whether you've disabled fields - you may choose not to show impact, urgency, or allow attachments - and what Custom Fields you have created.

Ticket Hub Agent View

Agents who are creating tickets get given additional options for who the ticket should be assigned to and who they're raising it on behalf of. Agents may not always be raising tickets for them, they may be raising it on behalf of a customer who has perhaps phoned into your support department.

Via Email

On the list of Ticket Types you will see whether Inbound Email Address is enabled or not and what the email address is per ticket type. If an email is sent to this address then it is turned into a ticket, using the subject line and body of the email as the title and description of the ticket. The default impact and urgency for the inbox will be used.

via Public Portal 

Customers may also create a ticket via your Public Portal if you have made a Ticket Type available through that and have the portal enabled.

The form works the same as the Ticket Hub Customer version.