Question I have is... what is make model of this computer so we can see what specs your working with. For example just because a floppy disk will boot on the system showing Windows 98 DOS environment, this doesnt mean that the system its booting on will support 98.
You will need the Windows 98 CD and a key to go along with this floppy to boot and install Windows 98 if the system isnt capable of booting off the CD. Some 486 computers fall into this category where they do not have bootable CD Rom support, and so you need to boot from Floppy which then mounts the CD ROM driver, which then allows for setup.exe to run to install Windows 98 to the hard drive. Once Windows 98 is installed to the hard drive most of the time the CD ROM driver is installed automatically from the Windows installation with MSCDEX installed etc.
Biggest concern for Windows 98 support is what CPU the system has, how much RAM, and size of the hard drive.