How to get the letter of commitment of the host institution for ERC Calls? For applying for European Commission grants, specifically ERC ADVANCED GRANT, I need to get an official letter from the host instuttion that they support my proposal.

How is the procedure to get this letter?

Do I need to contact the institution research office OR I need to find a collaborator in that institution to recommend me to get that letter?

Do they need to review my detailed proposal to decide if they want to support me OR they review my CV only?

How long does this process take?
If you want another institution to provide you with space, office, computer access, mentoring, etc, then they will need to know and approve of your proposal. Every university has a sponsored research office (or other name) that is in charge of these things. Contact the department head or the university you want to host you to provide you with the necessary contacts.