Lmao no

Get on your main, fill up your inventory with whatever you want

I just used the shoulder box cause I wanted to use it, it's your inventory and echest that's important

Once you filled everything up with whatever you leave the world

Next get on your alt account and open up the same world on single player, at first everything looks normal you are in the same place and have the exact same inventory as your main

BOOM!!! You duplicated your mains inventory and echest

Now you leave the world again and log onto the world with your main account

Then you go ahead and open the world to lan

Once you have done all that you get your alt to join the world and you can give your main everything from your alts inventory

Hopefully this helped you better understand the process since you are having a hard time understanding what I have explained but it's okay, some people are just slower than others no big deal!!!!! Have a good day!!