Common law relationship the home was in his name only. (although I was listed as a garantor)
He sold the house, taking back his initial investment down payment and paying off all of our joint debts. We split the remaining money equally.
How do I claim/file this amount and where?
As this is a Principal Residence, the sale is required by CRA to be reported on your tax return for "information only, and you do not pay tax on it.
If the home was in his name only, the sale should be reported on his tax return only. You are under no obligation to report the sale or any proceeds from it you received.