how do i add items that they drop for players to collect

as i bought the paid raidable bases 

Murderer / Scientists Items Dropped On Death

in the profiles

if you want it to drop a kit then use NpcKits plugin

i cant find it

it's in the profiles. just search for dropped on death

with the premium raidable bases do i need to install the free one for it to work as i can get the free one through gtx mod installer and when i try to use the premium one it only shows easy bases all the time even when i went into the file and put the bases name i want to use on the premium raidable bases 

install the premium version only. installing the free version is going to delete all of the premium features from the config and datafiles. they do not exist in the free version. you will have to reconfigure everything now

you must configure the difficulty by changing it in the profiles, not by renaming the base files.

oxide/data/RaidableBases/Profiles/

"Difficulty (0 = easy, 1 = medium, 2 = hard, 3 = expert, 4 = nightmare)": 0,

i got the premuim from codefling so i dont need to install the one from umod correct of the raidable bases plus i cant find npckits mod

correct, do not install the umod version. that is the free version.

google it. its on codefling

i bought it from codefling the raidable bases but i cant find the npckits mod anywhere

go to codefling or google and search for it. its the very first result on both sites.