Developing​ a simple web-app for salaries

I have a question and appreciate any help. So I have a project of developing a web-app that is similar to an ERP system. But with one single function, which is readung the basic salary of each employee, qnd deducting the amount spent at the cafeteria to the final receivable cash.

Here are the points to be done;

1 - the database (I already did that part). 2 - create a web app. A - each employee will have access to his/her own pay slip info. B - the admin will see all, and can add new accounts on demand.

My problem is; I don't know where to start. So please any help would be much appreciated. Even if pointing me towards a place that would teach me. I am running on a tight schedule of only 15 days. And I have very good apprehension of programming.