First install and compile the emulator as detailed in
https://twiki.cern.ch/twiki/bin/view/CMSPublic/SWGuideL1TOfflineDev#Work_flow_for_cms_l1t_offline_de
The steps are copied here for completeness:
cmsrel CMSSW_7_1_0_pre8
cd CMSSW_7_1_0_pre8/src
cmsenv
git cms-merge-topic --unsafe cms-l1t-offline:l1t-devel-$CMSSW_VERSION
git checkout -b mydevel-branch
scram b -j 4

Then, outside CMSSW, install the wrapper code by first cloning the repository: 
> git clone git@github.com:jbsauvan/L1TEmulatorWrapper.git L1TEmulatorWrapper
> cd L1TEmulatorWrapper
Compile the wrapper library. Make sure cmsenv has been called before compiling, otherwise it won't find the CMSSW emulator headers and libraries.
> make
The library is created in lib/
Finally set the environment variables with:
> source wrapenv
This will define the wrapper base directory (in EMUL_WRAPPER_BASE) and append the correct library path in LD_LIBRARY_PATH.

At each session where the CMSSW emulator is used through the wrapper, the environment has to be set with:
(1) 'cmsenv' in the correct CMSSW area containing the emulator
(2) 'source wrapenv' in the wrapper area