@bharatvarma Thanks. Pixelfed is more similar to Instagram than Flickr.
You can just follow Pixelfed accounts here, from your Mastodon account, and interact with them.
By doing so you interact with Pixelfed users as they were Mastodon users (their posts will appear on your TL like toots and so on).
But if you want to use all the Pixelfed functions you have to sign up on a Pixelfed instance. Here you find a list of them: https://the-federation.info/pixelfed