See if this helps, and post back with further questions:
http://home.satx.rr.com/badour/html/upgrade.html

Basically, you just run Setup from within Windows 95, and choose to upgrade....install Win98 into the same folder as you currently have Windows 95.

When asked if you want to back up the old operating system, say Yes, so that you can revert back if you have a problem after the Windows 98 install.