You can change your timezone by going into the General settings and then choosing the Display tab.

Towards the bottom of the page you will see the Timezone field

You can edit the Timezone field by clicking on the three dots, once you do, you should be able to see a pop up window that will allow you to select your timezone. 

You can either scroll up and down the list and select your timezone manually

Or you can use the search function

Click OK to confirm and Save to save changes.