I can not configure a skeleton

Hello,
I have built 'my_site' with antimatter, all ok. I can log into my_site/admin and configure.
But then I'm testing with saturn skeleton (site name 'saturn'), and I can not go into "saturn/admin"

Hello,
Solved, I discovered that you need to install admin plugin in bin.

Another question with saturn skeleton: in the menu appear two items that do not correspond to any page: "Externak Link" and "Feed" How to edit those items?

You have them in user/config/site.yaml, as external links. https://github.com/getgrav/grav-skeleton-saturn-site/blob/develop/config/site.yaml#L17-L19

Feed is added if the Feed plugin is installed (https://github.com/getgrav/grav-theme-saturn/blob/develop/templates/partials/navigation.html.twig#L18-L22)

Thank you for your help.

Another question: in "site.yalm" I deleted

Intro: 'Hello, I'm Saturn. I'm proud to be a part of milky way '
Intro_avatar: avatar.png

But in the header still appears a line in the place of the avatar and a box without text
From where can you eliminate that?

The way you identify those things is to inspect that piece of page with the browser inspector, find an HTML class or ID that helps identify it, and search for it in the user/themes folder, with a code editor like Sublime Text or Atom.

That will give you the exact place that you need to edit.