Hi -
I spent about a month getting my not-towered Amiga 1200 connected to my cable line. I bought my 3-Comm card from a nice fellow that always lists on E-Bay for about $25 or so. He helped 100% of the way and made all the difference.
The card I bought from him came with an installation disk.
There is a card reset command that had to physically be moved to the S directory I think. Everything else installed automatically - after I downloaded the INSTALLER program since I'm only running OS 3.1
After that I needed to download MUI magic user interface, then Miami DX and lastly IBrowse. It took me some time to get everything installed and running right. Since you have OS 3.9 you might not need to deal with the bologna I had to deal with. Also your machine is probably faster, has more ram and a videocard I hope.
Best luck - this was probably not too helpful. Hang in there.
Stephen in NJ