locket, lock it

Locket or locket means a necklace or pendant that opens to hold a photograph or a memento of some kind, such as a lock of hair--
She still wears a locket with his picture in it, although he's been dead for years.
We bought our mother a locket for her birthday, with all of our pictures in it.

Lock it or lock it means to secure or fasten something with a device, one that opens with a key or a combination--
The door is open; make sure to lock it when you go out.
When you park the car, make sure to roll the windows up and lock it.

Now that you know that, you can say--
"This guest has a gold locket; she wants us to lock it in the safe while she's out."

Note--"locked" is the past tense ( yesterday, or some time ago) of "lock", meaning to secure or fasten with a device that opens with a key or a combination--
I loccked the door, but I think I forgot the keys.