OTB. i would like it on a month to month basis not one lump sum. how do i make those changes?

In the Provincial tab, look for ON-BEN. In this entry you are able to select lump sum or monthly Trillium payments.

Note that if you are only going to get the OST portion of Trillium, it will be paid as a lump sum upfront in July 2018 when you select Monthly payment. Otherwise it will be paid in arrears as a one time amount in 2019.