what to do with error codes?

hi guys i recently had my check engine light come up and i pulled the codes. the first one was p0031 HO2S Heater Control Circuit Low (Bank 1 Sensor 1)which to my understanding is just the o2 sensor that needs replacing and the second code was P0456 Evaporative Emissions System - Small leak detected, this one i have no idea what it means. i searched through the site and couldnt come up with anything relating to the p00456. anyone have any ideas what i should look for first? try and just replace the fuel cap maybe? and does anyone know where the o2 sensor goes and how to get to it? and last question aha once these things are fixed does the light shut off on its own or do you have to do it by the code reader? thanks in advance guys

 

any thoughts? lol anyone?