First prepare the new home.
Use at least a 5 gal. container but 7 gal would be much better.
Drill holes in the bottom and on the sides close to the bottom.
Fill the bottom 3" with gravel, then start filling with top quality potting soil (compost, with organic amendmends). Put your current container in the new bigger one and fill in all aound, just if you were going to plant the plant and container.
Then remove the smaller container. You now have the perfect size hole.
Lay the smaller current container on it's side on the ground and squeeze all around, to loosen up the contact between the dirt and the container.
Above the new container, tap the current container while tilting it almost upside down very carefully. The plant and most of the soil should slide out and you can carefully guide it into the hole you prepared.
Then use extra soil if needed to make sure it's snug in it's new home.
To avoid transplant shock, get some Thrive Alive or horticultural (NOT human) vitamin B-1. Mix according to directions and water with it right after transplant.