As DaveR says:
@unknownuser said:
Go to SketchUp menu item: Window > Extension Manager - click on Install Extension... Navigate to where you saved the RBZ file, select it and choose Open.
It's then auto-installed for you...
But I find you difficulty hard to understand...
You say you understand you need a newer version of LibFredo [from a message?].
So you must have aversion already installed ?
You must also have some of Fredo's Extensions installed to have got the message ??
So why do you have trouble installing the newer RBZ, when somehow earlier ones were installed ??