First, you're gonna need PKSM and PCHex++. Homebrew and CIA both work.
Next you're going to want to deposit your pokemon into the PKSM bank, save bank changes, save and exit.
Now open up your gen 6 game, (Alpha Sapphire, Omega Ruby, X or Y) with PKSM and get the desired pokemon from bank and put it into your box, save bank edits save and exit.
After that, open up PCHex++ and select the game you're using. Locate the gen 7 Mon and edit to your hearts content. save and press start to exit....
[Tutorial] How to edit Gen 7 mons moves with a combination of PCHex++ and PKSM
Next you're going to want to deposit your pokemon into the PKSM bank, save bank changes, save and exit.
Now open up your gen 6 game, (Alpha Sapphire, Omega Ruby, X or Y) with PKSM and get the desired pokemon from bank and put it into your box, save bank edits save and exit.
After that, open up PCHex++ and select the game you're using. Locate the gen 7 Mon and edit to your hearts content. save and press start to exit....
[Tutorial] How to edit Gen 7 mons moves with a combination of PCHex++ and PKSM