BBT - How do you do it?

Bailey • Stay Strong. 🖤 You got this. ❤️
I'm new to TTC. I have only been trying for two months. I just bought my BBT Thermometer. I recorded only two out of the four day this month (March). I'm not exactly sure how to use it and understand it once it has been recorded. Can someone please explain it to me. I attached my BBT Chart as well. 
The temperatures weren't taken at the same time each day, I've had +2 spike since the first reading on March 2nd.