Prof. Willow gives you tips when you see an object, such as PokeStops and gyms, on the map first time. Since he does not show up after that, players may want to know where to see him again. Here is how to call the professor to learn tips he gave us again.
1. Tap the Pokeball-shaped icon
Tam the Pokeball-shaped icon at the bottom center of the screen first.
2. Tap 'Tips' icon
Tap tips icon below the setting icon at the top right corner of the menu display.
3. Professor Willow shows up!!
The professor appears to tell you some tips again. He simply repeats what he had already told you when you find objects first time.