How to Fix a Roof Leak in Asphalt Shingle Roofing
This roofing video pertains to repairing a section of roof in asphalt shingles.

Another video at another channel on the same topic and task.
Practical Roofing Concepts:
How to Fix Roof Leak in Asphalt Shingles

There is another video at Project Bolony that goes into removing and replacing shingles.

:34 – Explanation of what is going on
1:45 – Tools and materials
2:30 – Getting started – finding center of the action
7:17 – Lifing tabs
9:45 – checking shingles
10:39 – applying roofing cement
15:05 – checking shingles above
16:23 – Applying roofing cement on more shingles
20:20 – Applying roofing cement on last two rows
22:05 – final comments