Unlike some libraries that require complex initialization, you define your pins directly when creating the virtuabotixRTC object.
myRTC.updateTime();
The library is an Arduino software library specifically designed to interface with DS1302 Real-Time Clock chips. (Note: Despite the ambiguous name, it is primarily intended for the DS1302, though it is often adapted for DS1307 clones). It was written and released by the Virtuabotix team to abstract away the tedious bit-banging and shift-register logic required to talk to these chips. virtuabotixrtc.h arduino library