How can I change a blog description to the title of my Instagram post using JavaScript and instafeed.js?

Question

i am trying to add my latest post of my instagram page in my portfolio as a blog the image of latest post is added sucessfully but the problem is I want to change blog discription with title of image so i add unique id in image tag which is institle1 but when i try to target it itis showing error of null property please ans....

var feed = new Instafeed({
    template:'<a href="{{link}}"><img id="institle1" title="{{caption}}" src="{{image}}" /></a>',
target: "post-one",
accessToken: 'accesstoken'
});

let instatitle = document.getElementById("institle1").title;

document.querySelector(".blog .content p").innerHTML = instatitle;
console.log(instatitle);

i want to change paragraph content with the image title