Ascendancy Passive Skill Points can be allocated in your Ascendancy Skill Tree once you have chosen your Ascendancy. Your Ascendancy class is unlocked by completing any Ascension Trial. In order to change your Ascendancy, you must complete an Ascension Trial to the furthest extent you have successfully already done so, and then interact with the Ascendancy Altar while you have no Ascendancy Passive Skill Points currently assigned. Trialmaster and Balbala will offer the ability to refund passive points while in rooms with Ascendancy Altars to facilitate this.

You can obtain 4 sets of 2 Ascendancy Points for a total of 8 in the following ways:
Set 1 - Completing floor 1 of the Trial of the Sekhemas or completing the Trials of Chaos with at least 7 Trials
Set 2 - Completing floor 2 of the Trial of the Sekhemas or completing the Trials of Chaos
Set 3 - Completing floor 3 of the Trial of the Sekhemas or completing the Trials of Chaos with at least 10 Trials
Set 4 - Completing floor 4 of the Trial of the Sekhemas or completing the secret challenge behind the locked door in the Trials of Chaos