You should contact the landlord to discuss this. The landlord can change details on the tenancy agreement and also add extra clauses.
It's best to contact the landlord rather than OpenRent. We would never change anything in the contract without both parties' agreement anyway, so it makes best sense to allow you to speak to the landlord directly without having to go through a middle man!
The landlord has editable control of the contract, so can make changes at any time via the website.