BBT question

Angela • FTM 😻❤️ with baby Charlotte 11/24/2022 she is beauty , but fussy girl 😅

Girls, when you check your BBT, how do you do it? Oral or vaginal? That confuses me a little bit . Today is my first day with the OPKS, but I want to learn also my BBT. Thanks in advance. ( I know I have to do it same time every morning and as soon I wake up from bed)