The sentence you wrote is mostly correct, but it can be improved a little for clarity and correctness:
Original sentence: With the right saddle and posture, you can easily ride a horse.
Corrected sentence: With the right saddle and posture, you can ride a horse easily.
Explanation: The original sentence is understandable, but it is better to put the word "easily" after "ride a horse" to sound more natural. This way, the sentence clearly tells us that riding the horse will be easy.
So, your sentence is good! Just try to put "easily" after the action "ride a horse" for better flow.