The first thing to be aware of is that you will probably need to pay a substantial fee to get out of the current contract with the agent. Read the document you signed.
The second thing to be aware of is how much you dont know. There is a lot of law and bureaucracy governing our sector and unless youre on top of it all you can lose your shirt. Id suggest joining a landlord association and doing some training if youre not already a member.
Openrent can provide you with the tenancy agreement and many of the first steps, but it is then up to you to know how to manage and possibly end the tenancy. My view is that no-one should be self managing without the requisite knowledge.