Download the program 7-zip.
Export the project from Construst to a "New Folder" on ur Desktop
Then use that file on ur Desktop to make a .7z file using the 7-zip program.
Then add the .7z file you just made back into the "New folder".
With the .7z file inside of the "New Folder" on the desktop, Make a .zip file using the 7-zip program
Then upload that .zip folder with the .7z file in it to ur itch.io page
.7z file + .zip file = Upload