Its not as hard as it sounds, although I found it a ballache as it’s just something else to do...
My accountant did most of the legwork, but basically we use NEST for the pension scheme. You need to first register as an employer with HMRC and then they’ll prompt you to set up pensions. You then need to register with pensions and then add in your employee details (NI number etc...) once you have.
Its then just a case of working out what your contributions need to be every month (again, my accountant does payroll and so does this for me as well) and it comes out of your bank account.
You have set them up intially on oensions whether they want in or not. Your employee will get an ID number, if they choose to opt out they can use this to do so but for the amount it actually is I’d be surprised if they did.
Got to be honest, I thought you should already be paying into their pensions if they’re earning over a certain amount? (cant remember the exact figure but its somewhere around £10k a year)