You can choose the amount you want to trade with on your demo account after you install it.
After you fill out your basic information on the registration page that pops up automatically, you can choose from a preset range of deposit values or enter your own.
Registering for a demo account with XM is completely free.
They want you to become completely comfortable with the financial markets with a practice account before you commit to a real account.
Of course their market specialists will be with you every step of the way with trading support.