To be eligible for the Registered Disability Savings Plan, you must:
Get your social insurance number.
Be approved for the Disability Tax Credit, and Canada Child Tax Benefit if you have a child under the age of 19.
File your income tax returns.
Choose the Holder (the person who makes the financial decisions).
Be younger than or 60 years old.
The Step by Step Guide explains each of these steps (plus a bit more) in detail.