hi
i was give a lemon tree to grow indoors, the labels says good for conservatories and balconies which is fine, i bought food for citrus plants, but i should i be doing anything else with it? im good with most other plants but this is new ground

any advise is welcomed, it has small fruits on it, when normaly would be a good time to pick them?
help please.
thank you
its an idoor variety