Installing and configuring VirtualBox on Kubuntu 22.04

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Hi,

I have installed Kubuntu 22.04 and an getting familiar with it and have 
some questions.

I was researching how to install Oracle's VirtualBox and the way is to 
go to the K-Menu and do a search.  It comers up with a .deb package.  I 
was able to install it no problem and I can launch it from the K-Menu.

1) Is the .deb a different repository?  When I do a package upgrade does 
it get upgraded?  How do I uninstall if I want?

2) I want to install the Extension, as suggested.  The docs I am 
following says click File > Preferences > Extensions > Add a new 
package.

I do not have extensions in the menu.

Any help much appreciated,

Keith