Hi Lorna and welcome to GoY unless you support the plants the weight of the fruit will pull them down. We will start to feed our tomatoes once they are flowering and starting to set fruit. But others have different views, which is good.

moneymaker is usually grown as a cordon-- that is keeping the main stem and not allowing side branches ( be careful not to remove the flower trusses)
and allow the plant to grow to 5 or 6 trusses, by this time mine ( on the floor in grobags) are taller than me, so yes they will need a strong support, If you are using a liquid high potash feed go by the instructions on the bottle-- its usually when the first truss begins to set and immature tomatoes can just be seen

many thanks for your help-. They are growing well now and I have supported them with canes. Got fruit on one so hopefully will have tomatoes.
Lorna