Dehumidifier in Conservatory

[Cyclewidow46]

I've recently rented a house which has a conservatory directly off the kitchen which we use as a dining / relaxing area (table/chairs/sofa etc).
In the conservatory there is a large electric dehumidifier.
Now, excuse my ignorance, I've never used one of these before, but when exactly am I supposed to switch this on? I'm assuming when I'm cooking when the windows steam up? Is there any other time?
I'm just not sure.

Can be used for excessive condensation on windows, removing moisture from air to prevent growth of mould/mildew, removes musty/stale smells in the air and I have a friend who uses it to clean the air for her son who has asthma.

Thank you. That gives me a bit more of an idea