First, select the Scripts tab:
Then, in the right panel, click over the field with the text: "Enabled" (or "Disabled", depending on the current state):
You will be able to select the state. After sliding to the desired state please confirm the selection:
Triggers that are enabled will have an indication in the list (left panel):
In the snapshot above, the triggers CP and TEST_MONTHLY are both enabled, whereas IMPACT is disabled.