My resources say I can put my 5th food and lumber but I can’t put them anywhere the square doesn..

Resource production buildings can only go in specific locations. Food has to go next to the designated 'Rich Soil' locations. Lumber has go next to the 'Logging site' locations.

Each of the specific areas take 4 of the production buildings so if you are placing the 5th you need to find the other plots for these in your city. There will be 3 areas in total for each resource type, although you many need to expand the city areas to unlock them.