Me hecho a la idea de que ... in English
I don't know if there is a particular way / expression in English to say HACERSE LA IDEA DE ALGO

Let me give you some examples:

1. Me hecho a la idea de que no vas a volver a casa: I "have made the idea" that you are not coming back home.
The meaning would be: I already know you won't be back and I am accepting it.

2. Ya me hecho a la idea de que no voy a ser yo quien interprete el papel protagonista en la obra de teatro: I "have made the idea" that I'm not going to be the one who plays the lead roale in the theatre play.
The meaning would be: I already have accepted and know that I am not going to be the person who's going to play the lead role.

Could it be: I HAVE COME TO TERMS THAT you are not coming back or I HAVE MADE MY MIND THAT you are not coming back.

Question

Me hecho a la idea de que ... in English
I don't know if there is a particular way / expression in English to say HACERSE LA IDEA DE ALGO

Let me give you some examples:

1. Me hecho a la idea de que no vas a volver a casa: I "have made the idea" that you are not coming back home. 
The meaning would be: I already know you won't be back and I am accepting it.

2.  Ya me hecho a la idea de que no voy a ser yo quien interprete el papel protagonista en la obra de teatro: I "have made the idea" that I'm not going to be the one who plays the lead roale in the theatre play.
The meaning would be: I already have accepted and know that I am not going to be the person who's going to play the lead role.

Could it be: I HAVE COME TO TERMS THAT you are not coming back or I HAVE MADE MY MIND THAT you are not coming back.

Answer

Come to terms with' is the best option, it really means that 'i have struggled with this thought, but finally i am ok with it.'

Made my mind up - this is about making a decision. It is more appropriate to say: 'i've made up my mind that I won't be coming back'. Again, you thought about it a lot, but finally were able to make your decision. You will not be convinced to change your mind.

Answer

ME HE HECHO A LA IDEA DE ... ¡Disculpadme! No me había dado cuenta de que había escrito el título de forma incorrecta