This is easily done, you just need to get your head around filters.
So create a new filter,
And in the first object selection box select the Change object - you want to display changes in your query results.
In the second object selection box select the Incident object - you want to filter based on an attribute on the incident.
On the next page, select all the fields you want to display in your tab
On the criteria page you link the results up to the incident - drag over the Category field from the attributes (which are the attributes of the Change object), select the Is Equal to Category ( or Is Equal to?? )and select the Runtime option. The attributes it displays here are the attributes from the object you selected in the second of the boxes on the first page. So you want to select the Category. and then add anything else you want - eg, status of the change etc.
(im writing this off the top of my head, so sorry if its not perfect)