If you do a search here on Lotustalk you should find some more info on this (use the Search function in the header). What you want to avoid doing is using any detergent-type soap or, to the extent possible, any soap at all even car wash soap, on the top because there is a repellant-type coating on the fabric and if you use any harsh cleaners you will begin to remove that coating).
I would first just wash the top (installed on the car) with plain water first, just lightly hose it down to see how much comes off that way. Add some light brushing if needed with a soft brush (but don't brush it in, brush it off/away). A little regular car wash product (in solution i.e., from your wash bucket) should not hurt, if hosed off quickly, but generally it's best to go with a product designed for fabric (not vinyl) tops.
There are several fabric top cleaner products out there, I use the products from Ragg Top.
As with all approaches to car care, use the least-aggressive methods first.
I use BMW convertible top cleaner and the repellant that helps with waterproofing. Got a discount on the products, and always used them with the Z3 roadster. The cleaner made the Elise top look like new.
Thanks for the help. I just ordered RaggTopp from Autogeek. I tried a forum search but I guess I wasn't using the right lingo. I applied Zymol cleaner and Pinnacle Souveran Wax and it looks brand new! My husband used the same combo on his cars and loves the results. Thanks for all the help.