For this you will have to download the needed packages from IBM website. They are not free to download and you need user/pass and license. I will not cover this part at all.
Assuming you have already the needed packages, read what follows:

# nim -o define -t lpp_source -a server=master -a location=/export/lpp_source/core/7.1/ -a source=lppsource_71-03-01 lppsource_71-03-04

# nim -o define -t lpp_source -a server=master -a location=/export/lpp_source/core/7.1/71-03-04 -a source=/export/mksysb/global/aix71000_64_os_0303_us_1.gbl.mksysb_iplno lppsource_71-03-04

Examples will be put soon. I am not able to find them now :)