Umm well you can't. That's like saying you're trying to put 2L of water into a 1L container. It just won't work.
Your only options are:
1) Re-compress your footage so that the quality is low enough as to make much smaller file sizes. Remember a 4.7GB DVD will only actively take about 4.3GB (so you need to give yourself some good head room). And Menus/submenus/etc take of space too. So if you're using any of those you have to even further reduce the bit-rate (so quality).
2) Go to a Dual Layer burner and author a dual layer DVD. This is the only way to preserve your quality frankly.
But just out of curiousity, as you didn't specify, what are you trying to author specifically? Is it a long film (what is the duration), are you trying to put too many short films onto one disc, do you have/need lots of menus, etc., etc. You have to give way more details if you want a more precise response.