Is there any way to post on Instagram from laptop?

There is no way to post on Instagram from laptop. You can never post anything from laptop on Instagram. You can log into Instagram account on your browser on laptop and can see all the posts from your followings. You can edit your profile, like or comment as well but posting is not available.

You can post only on Instagram app. Download the app and tap plus sign button in the center at bottom. Pick your picture, add a caption and share it.