The unique payment instructions and references for your tenants can be found under View payment instructions on the rents page of your tenancy.
We reccomend to reach out to your tenant/tenants to discuss them using these references moving forward and check they know where to find these.
Alternatively when manually reconciling a payment there is the option to select Save the rule which means future and currently unreconciled transactions with the same particulars will be automatically reconciled with the same category.