Is it possible to install .rpm and .deb [application] files in VL 5.8 standard ?
As root, open Midnight Commander, highlight the RPM, hit F2, choose the conversion option. Then install the resulting tgz the usual way.
As carsten says, there's no guarantee that the converted package will work on your system. After you install a package, run
as root at a terminal prompt. Then exit from root and as user type the name of the executable at a terminal prompt. Note any error messages.
In general, it's best to use Vector packages or if there isn't one, use something from linuxpackages.net or slacky.eu. If there isn't one there, try to compile the program from source. It's not as hard as it sounds. Converting an rpm or deb is probably the last choice.