We have a potted (Roma) tomato plant which is coming along nicely. People told us to get a tomato cage, so I did and set it up. Do I then need to manage how the plant grows into and around the cage? Or do I just let it grow on its own once the cage is in place?
Watch the plant and train it if necessary. If the plant starts climbing the supports on its own you won't need to do anything. However, if your plant is stubborn you have a couple of options.
If your cage is one with horizontal supports thread the branches through them so that they learn to climb up them.
If your cage only has vertical supports (a stake or a tepee type support) you may need to attach your plant to the support. To do this you can use twine (there are some biodegradable twines out there), twisty ties(you can buy a bag of green ones for not much money), or small pieces of Velcro (this is what I use for my tomato stakes, I like it a lot, one roll has lasted me into the second year, I bought it at Home Depot last year).
Basically you just need to see what your plant is doing. If you have horizontal supports on your cage(which it sounds like you probably do) then your plant may just behave and you may not have to do anything. However if your plant does not want to behave just gently train it to do what you want it to do.