Edit in JSFiddle

var thng = {"name": "My Smart Coffee Machine now",
            "description": "Coffee Machine in my room",
            "properties": {"cmd": "done"},
            "tags": ["demo", "wot"]}
// DO NOT DO THIS IN PROD! This discloses your secret API key, instead
// work with run-time delegated auth, see: https://dev.evrythng.com/documentation/api#apps
// and https://github.com/evrythng/evrythng-js-sdk for examples.
var apiKey = 'YOUR KEY HERE BUT SEE COMMENT ABOVE'
$.ajax({
    type: 'POST',
    url: 'https://api.evrythng.com/thngs?access_token=' + apiKey,
    data: JSON.stringify(thng),
    contentType : 'application/json',
    accept: 'application/json',
    success: function(data) {
        $('#thng').html("Thng id: " + data.id + " Property: " + data.properties.cmd);
    }
});

<p><div id="thng"></div></p>