Use the search feature here to find more details, but basically you'll:
1. get a 2.5" to 3.5" HDD adapter (a.k.a. 44 to 40 pin IDE) - got mine cheap on eBay
2. plug in a bootable hard drive that has Win98 lite, the tools required to install it, and Juno on it (borrow your PC's HD if necessary).
3. configure the WP BIOS to boot from the HD
4. Boot from HD into command-line only mode & install W98lite on the DOC
5. switch BIOS back to booting from DOC
6. boot from DOC and install Juno from still connected HD
I won't bother going into any more detail - it's all been said here before and is where I got my info. Just pay close attention to how to take WP apart and read ALL of the various people's descriptions before you do so you have a good idea of what to do - I found details missing from most descriptions, but all taken together it went pretty smoothly.