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thanks well U I am new here .please tell me how to follow and upvote anybody

He's not actually following you, it's a spam reply he put on a bunch of people's posts.

....However, to answer your question, just click on someone's name and that opens a small window where you can click on their image to see their profile, click on 'follow' to follow, or click on 'mute' so you don't see their posts.

no bro I have my channel also on YouTube,well I am new here so don't know much about this platform