How is the pulse measurement performed?

At wrist. Typically pulse is measured at wrist by compressing the radial artery until a clear beat is felt. To be perfectly accurate when reporting beats per minute one should measure or a minute, but most will measure for 15 seconds and multiply by four. The pulse could also be counted anywhere the heartbeat can be felt - neck, chest, legs, abdomen, etc. Wrist is just easy.
Radial pulse. Feel for the radial pulse in your wrist (feel with fingertips as they’re more sensitive than other parts of your fingers). Pulse is located on the outer part of the wrist when your palm is facing the ceiling. Once you feel the pulse, count the number of beats in 15 seconds and multiply by four. Or in 30 seconds and multiply by two. Or just count them all in 60 seconds.