where starting the concluding part of the novel tess of the d'urbervilles

I'm not sure exactly what you are asking here. The conclusion or denouement comes in Chapter 59. Angel and 'Liza-Lu are in the county capitol of Wintoncester looking pretty haggard and forlorn. They stare at the prison and wait for the black flag to be raised. This means that Tess has been executed. They kneel and pray awhile. Then they leave holding hands and wander away in the bleak streets.

The actual conclusion of the book begins with Chapter LIII and ends with Chapter LIX;the section of the novel is called the Fulfillment.

Angel has returned after a trip abroad hoping that Tess will forgive him, only to receive her angry letter. Two are a mass of contradictions. For the first time, Angel seems to truly understand Tess, and he even defends her to others.

Unable to locate Tess, Angel approaches her family. When he finally finds her, she is under the protection of Alec d’Urberville. An altercation arises between Tess and Alec that results in Alec's murder. Tess returns to Angel, her true love and begs his forgiveness. They have five idyllic days together before the authorities surround their refuge. Angel hadn't thought Tess capable of murder; she in turn is relieved that the end result will be her death. She's never felt worthy of Angels love, and even their time together hasn't proven to her that she is. For her, their time was a gift.