Can't find extensions manager in latest version

I'm new to Contao so please don't judge me immediately :grin:
Can you please tell me where can I find extensions manager in Contao 4.3.5 backend CMS?
A screenshot would be very useful. I need to install rocksolid-custom-elements and rocksolid-slider so I can install Open Sauce theme after that.
This is the menu that i see.

Attachment 163

Thanks in advance!

Actually, there is no such thing as the old extension manager in Contao 4, and I am quite sure that there will never be an extension manager in the old flavour.

The team is working at a new, Composer based thing which will be called Contao-Manager, but at the moment there is no GUI for that. So, all extensions should be installed via Composer at the command line.

Maybe you will find a little more help in the tutorial you may find at https://rocksolidthemes.com/de/conta...e-installieren (in german language, but I think most steps are well explained).