You can access the settings dialog either through the app menu

SCLR app menu

or via the tiny settings icon in the main window bar:

SCLR settings

In the settings dialog you can define the font, colors for damage and heal and – most important – the default directory that contains the SWTOR combat log files.

SCLR settings

Typically you will find the generated SWTOR combat log files under

MyDocuments  >  Star Wars The Old Republic  >  Combat Logs