Hey there, next time ask in the "Help" section of the forums (here) To do this the best way is to get the plugin "Skript", restart your server, go into File Manager, click "Plugins" then click the "Skript" folder, go into "Scripts" and make a new file, name it give.txt or .sk, then paste this code into it
on first join:
give player 1 of ITEM HERE
then click save and go ingame and type "/sk reload give.(txt or sk, depending on what you did)"