We just found out that capital one place a lien on our home two years ago without our knowledge, we were never informed of any court date, how can this be legal and what can we do

You need to find out why this was done. One of the easiest ways would be to look at your credit report and see what notes are on it. If they somehow got a default judgement on you in a court then they received a award by the courts which would allow them to put a lien on your home.

Liens on real estate are recorded at your town hall.
You can pay off the debt and they will release it.

Did you have an account with Capital One? You may need to read your contract with them. Its possible you signed something that put up your home as collateral. Otherwise, the county will have the details of the lien recorded with the recorder of deeds.

Once you find out how and why they placed the lien, you can follow through and see whether you missed notice of a suit. If there was a suit and Capital One was awarded a default judgment or you signed a note putting the house up a, then placing a lien is legal. If there was a default judgment, and you never knew about the suit, then you may be able to get it vacated on grounds of improper service.

Did you have an account with them? Were you aware you default on it? How long have you lived in or owned the house?

ANY question on law needs to include your general locale as laws vary by area.