He's asking how to go about actually using this to improve his skills, which is something that I feel makes sense to discuss here as it's regarding his training routine.
I've just gotten this too, and there are a lot of things you can train on.
Practice L-canceling a shielded opponent:
Turn shields on infinite, set P2 to shield, shffl aerials and other attacks as you please.
Practice out of shield options:
Level 1: Go to practice mode. Turn shields on infinite. Throw down a red shell. Shield the shell and then wavedash out of shield or perform an aerial out of shield.
Level 2: Go to vs mode, pick fox or falco as your opponent. Set infinite shields, set P2 to perform spacie shield pressure. Practice your OoS options.
Practice chain throwing:
If you have a character that can chain throw a spacie, go to vs mode. Set a fox or falco opponent. I'm pretty sure the default is now to DI randomly, so you can either set a lvl 1 comp and just start practicing your chain throw, or you can probably set P2 to shield and practice like that. You can use the save state and load function to reset percentages, just make sure not to do that while your opponent is grabbed!
Practice tech chasing:
Computers now tech randomly, so you can practice tech chasing on reaction. Set a comp opponent to lvl 1 and start tech chasing. This is also good for teaching you to react to a lack of teching.
Practice Power Shielding Falco Lasers:
Set shields to infinite. Set the Falco to shoot lasers. Try power shielding.
Practice SDI'ing Fox's uair:Set Fox to perform the dair > grab > uthrow > uair string. Practice SDI'ing the first hit of the uair. Reload the state if your percentage gets too high.
Practice movement:
Select just your character, then force load stage select. When you pick the stage, use the command to set the camera to be a fixed camera. Practice movement around the stage.
Much, much more!
There are so many other things you can do with the hack pack, but this is some of the more obvious (and great) things you can work on with it. I'm sure people will find creative ways to use these tools and hopefully they will post them so everyone can train more effectively.