Remove covering for oil change

I have a 2003 1.8L Passat, how do you remove the covering from the bottom of the car? Is there a certain tool I have to get? Help!

I use a 10mm nutdriver for the front center fitting, and a wide flat-bladed screwdriver for all of the others. BE SURE TO SAVE ALL OF YOUR OIL AND FILTER RECEIPTS AND KEEP ACCURATE RECORDS OF DATES AND ODOMETER READINGS, if you do your own oil changes, to avoid losing warranty coverage!

I am the third owner of my car and most of the "screws" are missing. I use zip ties and the nut in the front along with what ever is left or replaced by the misc. shops that must have serviced this thing for oil changes. (My husband delivers auto parts and this is a regular thing that is replaced also, I've read lovely posts about them flying off while driving down the highway)!