help pleae so bumpy

how and where would i install rear springs in my towncar i cant just take out the air ride and put sptings inplace do i have to get the seat* for the spring to sit on or what someone please explain this to me how the springs would go on

The conversion kit springs are designed to fit into the upper and lower cradles. If you go with some other vehicles coil springs, you might have fittment problems.

Look here for a general guide:
http://www.arnottindustries.com/file.asp?Manual=TRUE&ProductID=6&Size=SMALL