The “About” page would be one place you could post your reflective “letter” or portfolio introduction. The other obvious place is in a post.
If you place your reflection in a post, I would recommend that you say a bit about your self here.
If you place your reflection here, you can also make the “About” page your front page. Just go to the Dashboard, then to Settings, and then to Reading, and you will see that the first option is where you set the front page.