I've done something I deeply regret. How can I seek forgiveness?

Bismillah. Yesterday, I committed a sin that feels so heavy on my heart. I'm not going into the details, but it was a major misstep, and the guilt is overwhelming. I feel like I'll be seeking Allah's forgiveness for the rest of my life because holding onto this shame is unbearable. I just want to turn to Allah, make sincere tawbah, and pray that He can forgive me and help me move forward. Please, any advice on seeking repentance would mean everything.