I guess I may as well describe to Nook Miles Ticket you how cash trees operate, whilst I am thinking about it.
So, have you ever encountered a bizarre gold glowing spot on the ground on your island? Dig it up, and you're going to find a bag of 1k bells, and the hole will be shining gold.
So, now you have a magic glowing hole in the own island, the next step is to choose the number of bells you want to plant. As soon as you've decided the number of bells you want to plant, you then will need to get a bell bag (comprising that many bells) prepared in your stock.
If you do not understand how to do that, open your inventory, pick the thing revealing the number of bells you are carrying, press A, then choose how many bells you want to put on your pockets.
Once that's done, go back to the luminous hole. Grab a shovel, open your pockets, then select the bell tote you would like to plant, and plant which at the glowing hole.
Now, rather than a glowing hole, you'll now have a nursery money tree. I'd recommend digging it up and moving it someplace convenient to reach, but you do not have to.
The money tree grows as quickly as every other tree, therefore, on Animal Crossing Bells For Sale the 4th day of its presence, it'll be fully grown, with bells hanging it off, ready to be harvested.