This is my experience...if you successfully finish at signalling school you'll be posted by the training manager to a particular workstation at WMSC to train on (which could be anywhere within the WMSC, unless you've been recruited for a particular role). Bearing in mind, as
@BrummieBobby says each workstation works different shift patterns. You will normally have to fit in with a particular signaller trainer and fit in and around anyone else training on that workstation as they wont want more than two of you sat there. You'll then be required to spend time learning that workstation under the guidance of your trainer who will tell you what to do and when. You'll also need to be aware that not every signaller posted to that workstation is a trainer/or wants a trainee sat next to them, so you have to respect that.
If you've joined there on a fixed term contract you should be applying for jobs whilst in training, either before passing out of signal school or whilst training on the job in the WMSC it doesn't matter when (and there are usually plenty of internal jobs up for grabs on the internal vacancy list every now and then). If you go through all the interview processes (again) and are lucky enough to be offered a permanent position then you will normally go to that workstation to train at an agreed time (or stay on the one you're training on if you've applied for a job on that one and been successful). All trainee signallers are then expected to pass out on the workstation by showing a certain level of competence usually within 6 weeks-but there is no rush to pass out as there is lots to learn. Until that time you will stay on the training pay that you were recruited on albeit any shift enhancements will still be paid extra.
Depending on whether you have a resident signaller position or relief role will normally depend on your roster and what you are paid. You also need to bear in mind that new signallers are usually expected to be relief signallers for a spell (unless told different) which means that you wont know your roster any more than one week in advance other than the rest days.