Click the banker and select open bank box:
Pick the deposit into secure account option:
Type in the amount you want to deposit (print screen didn't capture the input gump):
As you can see, the journal tells you that you deposited x into your secure account
Go to your wall safe. Tinkers can build it, it has to be locked and secured in your house. Make sure it is security is set to something the character from your other account can access:
Go to your wall safe (tinkers can build it, it has to be locked and secured in your house):
Double click it, click deposit and type in the amount (print screen didn't capture the input gump):
Log in with the char of your another account and go to the wall safe:
Double click it and pick withdraw:
There is a very important bit here. The secure account isn't shared among all chars in your account. They are exclusive of that char.
Head to the bank with the char that withdrew from the safe, click the banker and pick open bank box:
Select the withdraw option, type in the amount you want to withdraw:
The gold is now available for all the characters in that account to use it:
Phew, that was quite the process to do it.
Do the trade route when you can instead.