How can I add a new SQL Server in SQL-Server?

As you can see in the title, SQL-server is not very clear when it comes down to naming their objects. My situation is: I have two logins, "SQLExpress" and "SQLExpress01", and I want to add a third one "SQLExpress02". I tried using "Microsoft SQL Server Management Studio" but I didn't find a way to get it done (I remember needing another program instead of the Management Studio, but which one). So I tried "SQL Server Configuration Manager". This, however, gives me the opportunity to view the "SQL Server"s, but not to add one, as you can see in this screenshot: So I looked a bit further and I found the "SQL Server Installation Center". But when I tried adding a simple "SQLExpress02", I got the request to add the CD with the installation file. **??? I just want to add a "login", not perform an entire installation.** Obviously you can say "*You're an idiot! SQLExpress and SQLExpress01 are not logins, but SQL Servers.*" This part I have already understood, but honestly I don't care about the correct naming, I just want to know how to add one. Does anybody have an idea? **Edit, trying to give more explanation:** Some people refer to the term *instance*, which seems to mean that an installation, like an image.iso or setup.exe or something might be required. This is not the case: When I started working here, there was an SQLEXPRESS "login" present, and one of my colleagues used a different tool than the SQL-Server Management studio to add SQLEXPRESS01 "login". (I'm placing the word "login" between brackets because I know it's not the correct name). While searching on my computer for other SQL-Server related programs, I found the "SQL Server Configuration Manager", where SQLEXPRESS and SQLEXPRESS01 are mentioned as "SQL Server" objects (whatever that might mean). That "SQL Server Configuration Manager" gives the possibility to view those "things", but not to add a new one, which is exactly what I would like to do. I can't ask that colleague anymore, he has left the company, so I need to find it myself, hence this question here. If your reaction is "*Dude, you call something a "login", a "SQL Server", a "thing" and an "object" at the same time, you have no idea what you're doing, right?*", I can only confirm that: I have a past in dBase3, Oracle, Progress and MySQL but SQL-Server is completely new to me. Thanks in advance