Deploy WAR file on Spring - Tomcat 9

I have been tasked with the deploying of a WAR file on Spring boot (or Eclipse or any other IDE). I need to open the server proyect to edit the code and add new http request. Actualy I have no idea how to do this and I have no much information about this task and any solution idea.

I have been able to run the WAR file on Tomcat following this steps:

1. Download the Tomcat 9
2. Execute the .exe and intall the server
3. Paste the WAR file on /webapps
4. Run the server

Tomcat 9 shows this code:

So I suppose that the IDE I need to deply the WAR file in, is Spring boot v1.3.2

I downloaded Spring Tool Suite 4.9.0 and I install the Tomcat 9 server:

This is my configuration:

Now the Tomcat is runing and I can accese to http://localhost:8080/ but I don't know how to continue. I'm trying to import the WAR file to Spring but I don't have the web import option:

How could I continue? I made any mistake un to now?