If you mean literally how do you collect rent then I would talk to an agent about handling the properties for you. If you mean how do you collect rent when there are in effect 8 landlords then that is a different matter. Open a bank account, possibly one for each property - talk to your bank about this. Decide who out of you will manage the properties. Talk to an accountant about tax, allowances etc.
If you know what youre doing as a landlord then there is no need for an agent. An agent has no extra ways of getting the rent out of non payers than anybody else and many arent that bothered as they will still collect their fees even if the rent isnt paid. Use an agent if you dont know about letting and the law.