You can use Set Variable: Set To Random, that sets the variable to a random parameter, to do it:
When you want to spawn the player, place a Set Variable: Set To Random (should be in the first category), in the 1st slot put a variable (preferably a LOCAL one), let's call it tp_loc, and in the rest of the chest, you can put your locations of the expected spawn points. Then place a Player Action: Teleport and put the same tp_loc variable in the 1st slot and you should be good to go.
You can make the locations totally random using other blocks, but I don't recommend it as the player may spawn in an impossible to reach location, or in lava or water or stuff like that.