Hi and welcome @THE.WHAT 
I checked out your project, https://glitch.com/~local-world, and here’s what I found.
Your site is setup as a ‘static site’, that makes it easy for linking to other pages.
First let’s talk about what you’re linking to. It looks like you accidentally created a folder called ‘Homepage.html’ and nested some of your pages in there. I would drag them out of that folder so that they sit at the same level as index.html
.

Then, usually the way to link to another page is with an a
tag like:
<a href="Login.html">Login</a>
But I see you want buttons. You can style an a
tag to look like a button, which would be the “right way” to do this.
In that case, you’d make a style something like
.btn { border: 1px solid gray; padding: 4px; }
and then change your tag to <a href="Login.html" class="btn">
Now…
You can do the following but it’s kind of non-standard:
<a href="Login.html>
<button>Login</button>
</a>
Then there are some more exotic ways as described on this SO answer: html - Can I nest a <button> element inside an <a> using HTML5? - Stack Overflow
You also asked “How do i make the code in these pages?”
The answer is to open the corresponding file in the left nav bar (the one I pictured earlier) and put a load of HTML in there.
Just remember that at the moment, the address of your other pages is like https://local-world.glitch.me/Homepage.html/Login.html and you need to fix that first by removing the folder you added by mistake.
Have fun! Let us know how it goes!