Imposter Syndrome is doubt about what you have done and what you can do and usually shows up through anxiety and accompanies perfectionism.
If you want to increase your anxiety:
Approach new challenges believing you are out of your depth
Don't be yourself when working through problems
Avoid being honest about your experience
If you want to decrease your anxiety:
Start with honesty
Be yourself, nervousness and all
Reflect on your past wins and how they lead up to now
3 Steps to overcome Imposter Syndrome:
Breathe. Take two breaths through your nose (one short small inhale after an initial large inhale) and release through your mouth. A longer exhale than inhale slows the heart and reduces stress - it is called the physiological sigh.
Reflect. Think back on your biggest wins, the circumstances you overcame, and the final triumphant results. With your track record in mind, think about your current problem and put it into your personal historic perspective.
Get started. Know you may stumble and stutter, but you will improve with practice and consistent effort (just as you have in the past). Forgive yourself for making mistakes and continue to work towards the goal.
When your progress slows or you feel overwhelmed start back at 1 and work through 3.