I bought a house a little while ago and could not get approved for a mortgage so my father-in-law took out the mortgage for me and I’m paying the bank monthly I recently heard that I need to write a heter iska what would be the process for me right now?
Yes, this requires a heter iska.
The reason for this is that you have effectively borrowed money from our father-in-law, and you are paying him interest payments on the loan. True, he is paying interest on his loan to the bank, and you are merely “covering his costs,” but each loan is separate, so that there is a problem of your paying him interest.
You need to redefine the loan, or more precisely to close the original loan (he can simply forego the debt) and create a new loan, for which a heter iska will be a condition. You can use a standard heter iska document for this purpose.