Facebook live now a days is online feature which team activated a week before. its a great feature for covering events, live shows and real life stuff. if you are a helper or a teacher you can teach your users online with this feature.
if you want to use this feature then all you need is nothing. yeah on android Facebook you will see this option near create post button. simply click on it and you will go live in 3, 2 and 1. good thing about this feature is people can comment too.
users can like your video and also can comment plus can share live video of Facebook with friends too. so if you are not knowing about this feature check it out. but you need good internet speed to use this feature else it will disconnect you.
if you are not having this live button option on your android Facebook then do not worry. there could be 2 things, first is your internet is slow and second thing you can do is to clear Facebook cache from mobile settings and update it to latest version.
thats all for now have fun.