Can anyone tell me how I can get the effect of water running down objects i.e houses, steps, terrains?

Woah!... Lots of ways. One suggestion for smaller items such as steps is this... Successfully used in the image here. Save the object as an obj file and create a rivulety transparency map for it with UV mapper. Load the new mapped object into Bryce and position it just above the original mesh. With the trans map and suitable texture and bump applied, you will have nice water following the shape of your steps (or whatever.)

If you want to show a larger wet surface, copy the object and move it up a tinsy bit. Make it mainly transparent with a tiny bit of reflection and Bob's your uncle! A wet surface!

Yes that's exactly the effect I want, but very new user to Bryce 5 and can't seem to get the hang of it.

Lindans don't worry... we've all been there. Have a go and post an image if you get stuck or can't get the right results... you'll get loads of good advice and POSITIVE critisism/suggestions here. There are so many related techniques and skills to learn! Also have a look through the miriad tutorials here and on the rest of the web...