I did casual labour, was paid by the hour and got no T4. Income tax was deducted from gross pay. Where/how do I claim the income, and where/how do I claim tax deducted?

If your employer deducted income tax (or any other contributions such as CPP or EI) they are required by law to issue you a T4. When you have income tax or contributions withheld from your pay, the employer must remit them to CRA and you will be refunded if you have overpaid when you file your income tax.

If you have a copy of a paystub from your employer, have a look at it and see exactly what type of deductions they have withheld from your pay. If you cannot get a T4 after trying your best to get one, and CRA does not have a copy in their records, they suggest you file a T4 with the information you have from your paystubs. 

You can also file a complaint with CRA for any employer who does not issue you a T4.

https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/tax-slips/a-copy-your-tax-slips.html