Use a variable called "lootchance".
Lets say you click a button, set "lootchance" to random(1,100)
After that when you want the player to get loot, you add a condition checking what number "lootchance" is set to,
if equal to or lower than 82.87 > Give player loot common
If equal to or higher than 82.88 BUT lower than 93,24 > give player loot rare
if equal to or higher than 93.24 but lower than 98.42 > give player super rare
if equal to or higher than 98.42 but lower than 99.46 > give player Epic
if equal to or higher than 99.46 but lower than 99.98 > give player Legendary
if equal to or higher than 99.60> give player Super Legend
Prob a better way of explaining and doing it, I'm drunk, hope it helps anyways, merry christmas.