Tap an Oak Tree with a Tapper
Wait for the Oak Resin to be produced
Collect it from the Tapper when ready
Use a Heavy Tapper for faster production
Place Tapper on Oak Trees in your farm or the forest
Check the Tapper regularly for harvest
Buy Oak Resin from the Traveling Cart when available
Receive Oak Resin as a possible reward from the Statue of Endless Fortune on some days