Install OS again without mouse I have to install my OS again from scratch but the mouse/trackpad doesn't work in Recovery mode (I can't access a session to edit anything as the computer has no OS at all right now).

I managed to moved through the MacOS Utilities windows using cmd + F5 (voice control) and using Control + Cmd + arrows. The problem is that when I want to Reinstall a new copy of macOS after selecting the disc to use it pops a new window to fill the ID and Password of my Apple account, but I cannot access to this window using the commands shown before as it is not the currently selected window, so its impossible to write them.

What can I do?

I have a Macbook Pro 2008, in which I want to install el Capitan OSX
You may want to try to use the Tab key, and the Ctrl+F5, Ctrl+` etc., as advertised here: