there is a bug. ( or at least i think it is.) is where i can't see the menu for the stairs and stuff.
and i cant find the islands and sail
There are no islands or sails in this free Raft prototype. You'll need to buy the Steam version to get those and more.
Don't remember if the way it works is same in the prototype but in the Steam version you equip the hammer and hold right click to bring up the building menu.