Resident alien selling property abroad

Hi there, I have Spain citizenship and I own real state property along with my wife in Spain, that property used to be our primary home back when we lived there. No income has been gained out of it, now we are planning on selling it and some US taxation questions arise. As a comment, I have 3 years of paying taxes here. 

Before the queries, I have to add I have never reported this property on my tax return as I was told that was unnecessary. I pay taxes for the empty house in Spain, and Spain and US are holding an existing tax treaty among them. 

 

- Do I have to report the property on my previous tax returns?

 

- Once we get it sold, and after we paid taxes upon the gains, do I have to report the selling here in US as well?

 

- After that, the idea is to tranfer all that money to our bank account here in US, do I have to report it, and when?

 

Thanks in advance