How and what is the wrong order. "How" might be different based on the skill you are targeting.
First, answer "what" you want to upskill. Identify a weakness and/or an end goal you have that is currently hindered by lacking a skill. If you are actually asking for recommendations for you I would say interpersonal communication.
Onto "how": talent borrows, genius steals. Find how other people have trained that skill or look for someone with that skill to help teach you or to emulate. Some skills are just a matter of practice and repetition. Some require more finesse and identifying what specific hurdles you are facing and making sure your technique is good.