To arrive triumphantly. In the days of delivering freight by horse or mule drawn wagons, the teamsters would often festoon their rigs with ornate bells. If they became stuck or otherwise needed help from another teamster, they had to "pay" the one helping them get out of trouble by giving him or her some of their bells. Therefore, if you arrived at your destination without the help of anyone else, and perhaps even gave aid along the way, you arrived "with bells on."

Got the covid-19 vaccine

Ready to go full tilt. Possibly early version of balls out.

"with bells on" was first used in the Royal Navy and is in referance to a sailors bell bottom torusers. The uniform that included these trousers was their dress gear and was only worn when on liberty or various ceremonies like colours or sunset. It was also popular to wear this uniform to events such as weddings or funerals as it was proberbly the best clothing they possessed.

It's basically a way of exagerating the point so people know you really mean what you are saying. See example 1.

It can also be used as a sarcastic response. See example 2.

Used to add oomph to any phrase to simply reinforce your point.