If you’re getting married, they will require from your country of origin a criminal check on both, a marital status check, both birth certificates, full documents. All of this must be translated into Spanish by an official translator.
You have to ask for an appointment with the Registro Civil to start your “expediente”. Depending on their workload, they can give you a date to get married in 2-6 months.
You’ll also need two people to act as witnesses.
And both will have to swear before a judge that you aren’t being coerced into marriage.