How do I practice this!!

The cool thing about caged is that it allows you to do the same scale on different positions. Why is this cool? If you know all of them well you are able to switch between them in your solo. Why do you want to switch between them? Each position of a scale usually makes you come up with different licks(for me anyway) so it is a good way to not bore your audience by doing the same thing over and over again.
A good way to practice scales at first is just playing it up and down until you know it well. When you have done this you can start looking at arpeggios that are ‘hidden’ in the scale. When you know those you can combine the notes from the scale with the arpeggios to come up with some melodies and phrases when you improvise over a backingtrack for example.
Yes you can do some small little fills with scales people like John Mayer and Jimmi Hendrix do this all the time.

Take some time to master the caged system. Even if you feel confident with it. There are many ways to take it forward. You can learn sweeps this way as you can figure out the arpeggios easily with the caged system. It also helps learning scales faster as you figure out pretty quickly where you are playing the same notes you did further up the fretboard. So you figure out comfortable positions to play certain licks.. etc. It’s probably one of the biggest lessons on the site. It’s the trick that a LOT of good guitarists that I’ve talked to have no idea it even exists. Like, they know it but didn’t know the system actually existed. lol. Whoever invented the theory is a genius.