Posted: Wed Dec 12, 2018 8:54am
Hopefully someone with more recent experience will advise but, unless the system has changed, the first thing you need to do is register the S1s with an INSS office. The ones I know off the top of my head are at Elche, Orihuela, Alicante, and I think Santa Pola and Torrevieja.
Once they've accepted you onto the system, then you go to the medical centre and register and receive SIP cards. Then make an appointment for flu jabs. If you have repeat prescriptions in the UK, also make an appointment with a doctor to get those prescribed here.
I can't help you with medical centre times - I don't know the area. Where I live only has a small medical centre which is open from 8.00 to 2.00, but most of the larger ones are open all day.
There's a lot of information already on this forum, so it's worth spending some time searching or just browsing.