Within the Examples/LPCOpen subdirectory of your IDE install, you will find the LPCOpen package for the LPC11U1x family : lpcopen_v2_00a_lpcxpresso_nxp_lpcxpresso_11u14.zip
You might also want to check the LPCOpen pages for the latest package updates : LPCOpen Libraries and Examples|NXP
For details of how to import the LPCOpen examples into LPCXpresso IDE, please see the User Manual supplied within the IDE, or watch the videos at http://www.nxp.com/lpcxpresso
Note - for questions on the actual use of I2C on LPC MCUs, I would suggest posting into the "LPC" community, rather than the "LPCXpresso IDE" one.
Regards,
LPCXpresso Support