Do you have the purple stickman icon selected? The icons are filters and this particular one stands for characters. If it's highlighted and you wrote player, it should show the following: ImpPlayer FemalePlayer MalePlayer and FloaterPlayer.
If you want to add humans as playable characters, add either FemalePlayer or MalePlayer to the world.
To make them playable, you have to open the Sidebar, select your player characters and tick the Player tickbox such as the Global tickbox. Global makes characters well... global. It allows them to travel from map to map. Without this tickbox, said actors are just level specific.
Also, don't forget to give them a name, otherwise there will be warnings/errors in the log.