Which manual are you needing? The one which came in the original Warp 3 box? As far as I know, that manual was never available online.On the other hand, if you search the IBM Redbooks for OS/2, you'll be able to find a lot of information, much of which can be applied to Warp 3.
http://www.redbooks.ibm.com/
There are 2 specific redbooks which deal with Warp 3:
http://www.redbooks.ibm.com/abstracts/sg244552.html?Open
http://www.redbooks.ibm.com/abstracts/gg244505.html?Open
If you absolutely *need* the manual which came with Warp 3, consider e-bay. Usually copies of Warp 3 go for around $10 + shipping... Warp Connect a little more, but not much.
Hope this helps