Trying to attach resistor to MacBook logic board (a1278, 820-3115-b)
Soldering surface-mount components is tricky, and requires the proper tools and experience. Indiscriminate use of a heat-gun is more likely to destroy the mother-board than to fix the issue. Lumps of solder or burned traces may also make repair difficult or impossible.

The best solution would be to find an experienced technician with the proper equipment, such as an advanced student in EE or a computer-repair specialist to reinstall it.

If you insist on installing it yourself and can't find the equipment to use, you could try an electrically-conductive cement... but that might not last, particularly if you remove the board again.