Go to JIRA Administration → Issues → Custom Fields → Add Custom Field and choose STAGIL Assets Traffic Light.
Type a Name and optional a Description. Press Create.
Configure an Assets Traffic Light Field
Go to your custom field and click configure on the right side. Click Edit Stagil Assets Traffic Light.
Now you have the configuration screen.
Here you can choose JQL, current issue or based on relation of current issue. By defining the source of issues, you define the amount and type of issues, that you want to filter in the next step.
Here you can define conditions for each light, based on your selected issue source above. First you define the JQL and then optionally the quantity of issues which trigger the color of the light. For example: If there are more than 5 issues within the defined JQL queue, they all will be marked with a red traffic light. Besides this you can rearrange the order of the colors by sorting them up or down.