Firstly, you need to be aware of the legal side of raising the rent.
The easiest thing to reflect this change in rent is to create a new tenancy in the landlord software. This way each of the new rent requests will reflect the increased rent all other aspects of the tenancy will stay the same.
Re the 'raising the rent' item link: what it says is out-of-date in one respect.
It includes this bit: They can do this by going through the motions of issuing a section 21 notice for possession even at the start of the tenancy to ensure that a landlord can bring the tenancy to an end.
BUT that cannot now be done. The law has been changed.