Similar to SAGA algorithms don't work in QGIS 2.8 except that SAGA does not appear at all in the Processing Toolbox:
As a check, I used the Python Console with the following code to see if any SAGA tools are available (which they're not):
import processing
processing.alglist()
I've installed QGIS 2.8.2 Wien via the OSGeo4W Network Installer, 64-bit and downloaded the latest version of the Processing Plugin (v2.9.3).
Best Answer
Just to add to the earlier answer...
You can find the field for the path here -
Processing > Options > Providers > SAGA > SAGA Folder: