How do i start to work my beginner horse up to doing extensions and collections within each gait comortably?

I have a beginner horse and i want to be able to do extensions and collections within each gait. How do i do this? what should i be doing to work my horse up to this? i know it will take time and patience, and im commited to that. but i need help training my horse on my own. i cant afford a trainer, so i am my own horses trainer.