Install like any normal mod, put the "Lenwe Follower" file into your data folder in you game folder and make sure it is checked on the skyrim launcher under "Data Files".
Find Lenwe in the Sleeping Giant Inn in Riverwood.
NOTE: The sword he is using is a custom sword with extra damage, it is advised for more balanced play to let Lenwe keep the sword but you can take it for yourself if you want.