To dominate battles in Pokemon Go, approach and then select the
desired gym. If you match up well with the competition, press the fight
icon on the lower right.
When the battle commences, press either the right or left sides of
the screen to dodge enemy attacks, and then strike back. Do not get into
the habit of frantically tapping to attack or you’ll lose within
seconds. Dodge, wait for an opening and strike back… then repeat the
process.
Keep in mind that if you have low level Pokemon, claiming a gym in
Pokemon Go will be extremely difficult. It’s smart to level up your
Pokemon and then go after the gym. Patience!