Headaches are very common and the reasons are many. Often it is dehydration, malnutrition, stress, work, worry or anxiety, but it may be physical and related to or caused by muscular or skeletal stress to the neck, shoulders or back which relates to posture.
These videos are supplemental to your course instructions.
In this video the therapist is good, but a little rough and there are other techniques you could apply.
Also note that all the techniques taught cover these points with greater softness and flow.
In this video the therapist give a good explanation.
Headache Relief with Trigger Point Therapy