what went wrong? what did u do and where did u get stuck?
well, let me help u anyway, I assume that u already have ur mobile connected to the pc, either by cable or bluetooth.
You should have Nokia PC Suite installed, and then the .sis file would be an executable installer, and a double-click on OXMED.SIS would get it installing on your mobile right away.
If u don't have it installed, I mean the PC Suite, install it and it should work.
Another way is copy OXMED.sis to ur memory card, either by a memory card reader, bluetooth, IR, and then install it from the phone, u can delete the installation file afterwards.
I hope I helped