How can I discharge static electricity from my body?
You worry too much. Go to an area with least possible sources of static electricity, e.g. no carpet. The adapter most likely comes in a ESD bag. Open the PC and touch the PC metal parts while holding the adapter bag, take out the adapter, hold the metal bracket, touch the PC metal case again, and there should now be no potential difference between the adapter, you and the PC. Mount it in the slot and close the PC. Done.