How can I update a data in MockApi.io

I'm using Mockapi.io for my project. I want to update a attribute of a data but put function not working. I tried in Postman but the result is same.

"https://<I'm using my ID>.mockapi.io/todos/id" with this url I'm sending data below.

{
    "isCompleted" : true
}

But it's fetching the same data with same attribute below.

{
    "title": "test",
    "isCompleted": false,
    "id": "12"
}

How should I use it?