If you want to post any image or read your instagrammesaages on a browser, you need to click on developer tools first (which you can find under your browser setting). Once you see the inspect box, click on mobile icon which is visible on left top corner of your inspect box. After that input the url (https://www.instagram.com). Once the insta will open in your browser in mobile preview, you need to input your insta account credentials and thats it. You can use your insta account in browser. Now just read your messages or post images you can do all.