1) Create a table named tbl_Security_Level with fields fld_Sch_Num_PK (autonumber is fine), fld_Sch_description (text 15).
2) Alter your existing tbl_Empoyees so that a FK field for the foreign is added (join compatible with the preceeding fld_Sch_Num_PK field).
3a) Using whatever tools you can lay hands on (php of course, but also Dreamweaver and etc.): create a splash screen that prompts for user id (and by query) selects landing screen.
At a minimum, create and "Edits" screen through which you can edit the underlying tables (would need highest clearance) and crucially, an order taking screen. My approach is to create queries that will be associated with each action.
Please have all screens but the first reflect back who is logged in. Also, all but first should have an escape button back to previous screen and all screens shoul have a logout button (upper right of screen).