Ok so here's a dupe guide for CE.
If you dont know how to find character's addresses keep looking in this thread. probably around page 4/5.
I started by finding out the values for my shell Odin before the i went to look for a fight.
I also found the values for Marth even though i forgot to screenshot but you can see i found both values for Odin. Regular and in battle. I saved the one that i didnt have.
Thats the one you want to change.
I opened the calculator, set it to hex, searched for marth value, subtracted 118 and right click on the memory window "go to memory" and typed in the value.
As you can see i have my window just the right size for the addresses i need to highlight and the extra row is the original value i start with. DONT HIGHLIGHT THAT ONE.
MAKE SURE YOU'RE ON THE INFO SCREEN OF YOUR SHELL BEFORE YOU CONTINUE.
Now just paste them onto the address you found for your shell. your unit should turn red as well.
Now just win the battle and you should have your unit but you cant edit yet. Swap out weapons, close the game and reload.
Edit: Forgot to mention this but plz dont put your OP heroes on your first party slot. thats your arena slot. People will be banned but we need to be discrete about how we go about our cheats.