There are a few things you need to do in order to post a photo on Instagram on a computer. First, open Instagram and sign in. Then, click the three lines in the top left corner of the screen and select “Post.” In the “Post Type” field, select “Photo.” In the “Description” field, type a brief description of your photo. In the " hashtags" field, type #photooftheday or any other relevant hashtags. Finally, click the post button.