Start off by believing that something will heal - that God will heal it. Maybe something in yourself that needs healing, or in someone else.
Get a sense of how 'much' you believe this. How much certainty do you have? How much do are you so convinced that you have absolutely unshakeable doubtless certainty and zero fear?
Now, push your sense of belief into a whole other ballpark by transforming it into expectation. Adopt a perception of EXPECTING that healing must occur. Expect as strongly as you can.
You should notice a sense of your belief changing from 'just a belief' tinged with uncertainty, to a very focused, intent, direct, piercingly certain kind of 'demand'. It transforms into power. It transforms into a sense of REQUIRING that the healing occur. Of commanding it to occur. That it MUST occur. Be as convinced of this as you can.
When I do this I feel a sense of some kind of focus or something come down through my upper body down into my belly area. This could be Holy Spirit or your own Spirit.
The closer you can get to absolute certainty the more likely it is that you will start to feel Holy Spirit start to move and flow. The stronger the sense of expectation the better. It's okay to be practically 'demanding'. This is "Authority".
You as a Child of God have authority over all illusions. Another word for this is "dominion" (biblically, we are told we have dominion over the Earth - this is what it means). You extend the Authority of Christ in a kind of 'legal' way. You legally have the right to command illusions. To command sickness to leave. To command ego to be undone.
As such when you enter a state of firm belief and expectation, you are also joining with Christ. Being One with Christ is an important aspect of miracle working, and is also why you need to ask Jesus what miracles to perform and for him to help you perform them. You need alignment with Christ/certainty in order to perform them.
You also need to remain in certainty regardless of what physical appearances seem to suggest, regardless of evidence or lack thereof that healing has occurred, regardless of any kind of illusions or any signals coming from the ego world that suggest anything contrary to this firm conviction. This is why you must believe it in your MIND, in cause, and the illusion/body must follow to demonstrate what the mind believes is true.