fallout newbie. help me understand mods

first fallout ever and enjoying it so far! i think i've got the hang of the majority of the game and the system but i really really dont understand all the mods i pick up throughout the world. so say i have a mod to create a 'sharpness' on a baseball bat. how do i use it? it's not like a plan that i basically pick up and read and have access to forever. is it a one time use or once you 'use' a mod is it yours to mod your gear with forever, etc.

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someone please enlighten me. i'm a melee build but have 5 points in ability to craft modify melee weapons.

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thanks to anyone who responds.