You can access SmartTime in Designer either implicitly or explicitly during the following phases of the design implementation:
After Compile - Run SmartTime to add or modify timing constraints or to perform pre-layout timing analysis
During Layout - When you select timing driven place-and-route, SmartTime runs in the background to provide accurate timing information
After Layout - Run SmartTime to perform post-layout timing analysis and adjust timing constraints, as appropriate
During Back-Annotation - SmartTime runs in the background to generate the SDF file dedicated to timing simulation
You can also run SmartTime whenever you need to generate timing reports, regardless of which design implementation phase you are in.