You can definitely get Apprentice at
http://www.dragonstudios.com, since they make it.
To start Apprentice, click on File on the menu bar in the upper left and then New Game.
On this screen, Load Deck from one available, choose Solitaire, whatever you want your starting Life and Cards In Hand to be, then Okay.
You should be taken back to the main screen and on the left have the number of cards that you just chose in hand. Then you simply drag them over to the big playing area, double-click to tap stuff, etc. All of the menu options should tell you how to draw cards, add/subtract life, stuff like that. Click on the phases as you play to get used to it (like try not to draw cards during upkeep

).
Right-click on cards in play to set counters, attack, attack without tapping, etc.
The thing to remember is that this is all manual! The game doesn't keep track of mana when you've tapped lands, set counters when cards come into play, automatically draw cards for you, etc. It's just a framework so you can play someone over the Internet, but like a game in real life you have to keep track of everything yourself.