For me, it is an on-going process. Because I started that journey on the very bottom of things, it has taken almost 20 yrs to get to where I am now. And I still have a long way to go. I share that not to discourage you, but to let you know it is not something that happened overnight (in my situation).

The bottom line is to try to start finding just one thing about yourself you like in a day. Even if it is something you think is small such as "I am good at following up on tasks." And write it down in a special journal that will ONLY have these statements in them.

Every day, go back and read all the entries you have before. Read them aloud.
Do this just one time a day.
When you start to be hard on yourself for something, go to that journal and just randomly pick one thing to read.

Doing this will help you start to build those positive self acceptance statements.