G'day guys, I've got a 1998 magna wagon and are trying to install a rearward facing baby seat. I've read the instructions and done as it's said but it is really loose and I'm unsure as how to get it tighter. It's a mothers choice one if that helps. Any Ideas??

"Its really loose" is a very vague description

Are the top straps that attach to the anchor point loose, or are you not able to get the seat belt tight enough?
I got someone to lean on the baby seat, pressing it into the seat, while i tightened the seatbelt. you need to pull the bottom strap tight, before you can pull the upper part of the seatbelt tight because they rub on each other.

On the TL wagon, it states that the belt must be fully pulled out and then used, otherwise the seatbelt won't lock on tight.

The seat belt part is the bit that's loose I think. If I tighten the anchor strap too much it lifts the baby seat off the back seat.

Most baby seats require you to fit of these buckles on the car seat belt, so that you can pass the seat belt through the seat, and allows you to pull it tight... Also, placing a rolled up towel under the seat helps give the seat a "flat" base to work with.

http://img.photobucket.com/albums/v210/Grosvenor/T2eC16VHJHYE9nzpeCmBRKCuwcYQ60_35_zpsb8d62b2e.jpg (http://smg.photobucket.com/user/Grosvenor/media/T2eC16VHJHYE9nzpeCmBRKCuwcYQ60_35_zpsb8d62b2e.jpg. html)

Definitely use the buckle pictured above. Google how to use it correctly. Relying on the seatbelt tensioner alone is not good enough.

The buckle pictured though is hard to get tight in situ. Easiest to get it roughly secure, then remove car seat, tighten the belt slightly using the buckle thing above, then put seat back in.

Then sit on seat with all your weight and see if you can clip the seatbelt in with brute force. If it's too loose once finished, remove and tighten again.

Mine are absolutely rock solid (shaking seat causes car to shake). Probably not the best for the seat cushion foam, but my kids safety comes first.

Or you can get a professional to install it. Ring most shops that sell car seats and they will refer you to an installer.