How to contact the INSS:
-Internet: http://run.gob.es/solictarcita
Also www.seg-social.es
-Smartphone or tablet via the App. App
-Telephone: 901 106 570 / 91541 25 30.
for general information: 901 166 565 / 91 542 11 76
Telephone numbers above, be prepared to go on a merry-go-round of answerphone messages and new numbers. A pen a pad and Spanish essential.
You can also enter the website with your Clave or digital certificate.
With or without a digital certificate:
You can also make contact via their email for your region.
Making your appointment with or without a digital certificate. Enter the blue link above for social security procedures. On opening page scroll down and click on “cita previa”

Check all options but to make your appointment which can be a physical or telephone appointment, click on second box. See screenshot below.

Full Guide in Spanish:
Entitlement to:
-Healthcare cover.
-medication/prescriptions.
-TSE equivalent to the EHIC.
Receiving a Spanish pension and you wish to work, you should get in touch with the INSS.
In Spain there exists:
-Widows pension.pension
-for orphans. Pensions
-for invalidity.
-Pension non contribution.
When can you apply for a contribution pension?
Requirements:
Be 66 years and two months old and prove at least 15 years of contributions, of which at least 2 must have contributed in the last 15 years.
Be 65 years of age and prove at least 37 years and 6 months of contributions, of which at least 2 must have contributed in the last 15 years.
The retirement age can be reduced or anticipated in some cases (early retirement, partial retirement, people with disabilities, age reduction coefficients, etc.).
You can make your application online: