These are the preliminary steps.
First, you try to relax and clear your mind. You want to get other thoughts out of the way. Don't obsess on this, it doesn't have to be perfect.
Then you try to form the thought or feeling you want to focus on. Form a thought that represents everything. So, if you are focusing on "how I feel right now", you want one thought that contains the entirety of how you feel.
Then try to experience this thought. It could be a feeling in your body, or an abstract image, or anything.