Permission problems installing nginx

I’m following along with this article https://www.digitalocean.com/community/articles/how-to-install-rails-and-nginx-with-passenger-on-ubuntu. At Step 6, I’m getting the following message asking me where I want nginx installed to (I clicked return) and then got an error because I’m running the installer as my name ‘michael’ (which I gave sudo privileges) instead of root.

Can you explain what I’m doing wrong?

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Where do you want to install Nginx to?

Please specify a prefix directory [/opt/nginx]:

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Permission problems

This installer must be able to write to the following directory:

/opt/nginx

But it can’t do that, because you’re running the installer as michael. Please re-run this installer as root.