Hey, thanks for your question.
No specific work experience is required to apply, however you'd need to be able to demonstrate in having an understanding of the NHS . However you plan to achieve that, whether that be through work experience etc. is up to you.
For skills: I'd look at what sort of stream you want to apply for and see what skills are needed for those role and go from there.
I second what Aditya says, especially with regards to the specialism skills and interest.
I'd also say that for the interview and the assessment centre you will be asked to demonstrate competencies and the potential to develop leadership skills. For this it helps to draw on experiences you have gained (through employment, volunteer work, being on committees, doing campaigning, leading a group or team or a club).
I hope that helps.
Thank you for your feedback!