You should be able to drag the cards from your hand onto one of the squares with dotted lines (which are the locations you are able to build on). Make sure you have enough ⚡energy to play the cards (cost of energy is in the top right corner of every card, and the total energy you have is along the bottom).
Just so you know, this game was designed for screens that are 1920 x 1080 or larger, so smaller screens may hide parts of the UI, and it's completely unplayable on mobile devices. Apologies!
tryed zooming out to very silly results but even at defualt zoom huge open space no play spots