O2 Sensor quick question

Automotive/Jeep Enthusiast Rookie here. I just replaced the faulty O2 sensor and I was wondering if I have to do something to reset the sensor. The manual I used for the repair said I need to take it to a shop to get it reset through the computer. Is that true? Also, what does the sensor even do? Will it really improve my gas mileage? Thanks for helping out a rookie.

You can unhook the battery for 5 minutes or so this should reset things, or if the 02 sensor fixed the problem just driving it shoud eventually turn off your check engine light [I assume it was on]

thanks markatimber. yeah it eventually went off fyi.