If you don't see an AssemblyInfo.cs file, you can just add one. Right-click your project line in Solution Explorer and click Add -> New Item (or hit Ctrl-Shift-A).
In the small dialog that may show up, click "Show all templates". A larger dialog with all available file templates will show up. Find "Assembly Information File" and click it ONCE. Check the filename at the bottom of the dialog and make sure it says "AssemblyInfo.cs". Click Add.
The file will be created and opened for edit. You can find all the information on which assembly attrbiutes you can add to your project (really, just an assembly) at
here[
^]
Here's an example of how to add a Description and Copyright attribute to a test project. I just added the last two lines to the AssemblyInfo.cs file:
using System.Reflection;
using System.Runtime.InteropServices;
[assembly: ComVisible(false)]
[assembly: Guid("43256ce6-54a4-4178-b19e-e16829d728cb")]
[assembly: AssemblyDescription("This is a test!")]
[assembly: AssemblyCopyright("Copyright © Whoever 2023")]