Finish My Code: Beginner C Programming with Custom Data Structures and Simple Sort of Data in an Array

I'm learning to code in my free time and this exercise in my C Programming beginner's guide is giving me a lot of trouble. I have written some of the code, but I can't complete the rest even after many tries. I'm trying to write a program that asks the user for a date in the format of mm/dd/yyyy and then adds seven days to the user's date, printing both these dates out at the end. My problem is I am unable create a custom struct to store the date information entered in memory. I also can't figure out how to call a custom function that adds seven days to the user's date, passing in the data in and out of the custom function using the custom struct. I'm more of a visual learner, and upon seeing how the rest of the code looks will enable me to reconstruct parts of this exercise and then hopefully write one completely from scratch.