You tame them by droping ferti eggs from your inv on the ground. You need to do so when the snake is not aggroed, so sit on a rex or smthing it wont attack. Be sure to drop them from your inventory, not from dino ones, that will make it bugged, it wont eat. To a lvl 20 Rex egg gives 29% on 2x event, bronto 26.7% and giga and wyvern the same, looks like all the big eggs give approxymately the same amount.. so dont waste the best you have ? If they get aggroed on you just run away and return, taming wont drop. Happy taming!
When taming the Titanboa, firstly build a taming pen (google ideas if needed), drop a titanboa into pen. After this you can sit on top of the pen and throw eggs in front of Titanboa every ??minutes (depends on egg used for taming). Use an egg timer lol