If you departed on a VFR flight and you are instrument rated and the aeroplane is IFR equipped, and you decided that you wanted to break through some clouds
Sounds like your question should start "If you departed on a flight in VMC and you want to go IMC..."?
Assuming you're in Open FIR, just fly within the limits of your license and aeroplane i.e. in or out of cloud. And assuming you're getting a FIS from someone, see if you can't get better looked after with a RIS or even a RAS.
Otherwise, if you're in, say, Class D, you'll have some sort of clearance/routing to adhere to.