Read this if:
Family / other contributions
A subscriber (parents, grandparents, legal guardian / any person really) can open a RESP for you (the 'beneficiary') at any time and contribute money to it. The money will grow faster than in a taxable account because of the tax deferral (no tax on income in the RESP).
Canada Education Savings Grant
Under this program the government will contribute 20% of your family contribution each year, up to a maximum of $500 (and a little more for lower-income families). There is a lifetime maximum of $7,200.
How to catch up on the Canada Education Savings Grant
If you haven't turned 15 yet (specifically, you have time until the end of the calendar year when you turn 15)...
Calendar year when you turn 17 is the last year when this grant is available to you. If you're catching up, to be eligible in the calendar years in which you turn 16 and 17, you need to already have a RESP because one of two additional conditions must be met:
Canada Learning Bond
Students from low-income families are eligible for up to $2,000 under this program even if their families are unable to make RESP contributions (if the family makes a contribution, they'll also receive the the Canada Education Savings Grant).
How to catch up on the Canada Learning Bond
The last year in which you can get this grant is the calendar year when you turn 15.
Provincial grants
Some provincial governments have additional RESP grants. You should research them separately to see if you can catch up. The bank where you're opening or have the RESP account should be able to help you.
Government program rules sometimes change so always do your own research:
https://www.canada.ca/en/revenue-agency/services/forms-publications/publications/rc4092.html
You'll need to ask your parent / primary caregiver / grandparent / any person willing to help you to go with you to the bank and act as a subscriber for your RESP. This is necessary even if they are not making contributions and you're opening the account only to benefit from the Canada Learning Bond Program.
You'll most likely open a savings account or buy a GIC for a few years such that it matures when you go to a post-secondary program and will need the money.
Opening a registered account / buying a registered GIC is similar to opening a similar non-registered account.