Step 1 - Open the Disk Utility app
Step 2 - In the top menu go to File> New Image> Folder Image
Step 3 - Select the folder you want to protect with a password
Step 4 - Under encryption select AES 128 bits and create the password you want for the Mac folder.
Step 5 - In image format select read/write
Step 6 - Save your folder and you're done!