Assign to: select the support group to which assign the ticket. By default it is assigned to "Central support" group: you can address to it general questions, or if you are not sure about the right support group to which assign a ticket
Priority: the priority of your ticket
Subject: put a not-confusing title
Description: the details of your problem. Add any information that can help the supporters to debug the problem, like:
command used and its output
VO used (past the output of "voms-proxy-info --all"
site or service contacted
middleware version
Add file: the attache file filed
GGUS ID: ignore it
Category: select a category in the menu
Force Remote Notification: this field is active when you add a response to a ticket come from GGUS: you can decide whether send your response to GGUS or not
Responsible EGEE Support Unit: ignore it
In order to answer to a ticket, click on the "add a response" button: