Make sure you have installed development packages of SCIM, whose version must be 1.0.0 or above. Take Debian/Ubuntu as example:
Make sure you have installed libchewing 0.4.0 (or above version).
Now, it's ready to build SCIM-chewing.
Make sure you have alread installed SCIM-chewing, to see if the following file exists or not.
Set up SCIM, and specify the proper modules, such as XIM frontend, GTK+ im-module, and QT im-module.
Assign IM engine to Traditional Chinese/Chewing.
Have Fun!