1. In case new theme update is available, you will see the following notice in your WordPress admin area:

2. Updates also appear on the “Themes” page in your WordPress admin area:

and on the “Updates” page:

3. For the changelog just click the corresponding button and an overlay with updates history appear:

4. Before updating you need to read and confirm the following important notice:

Finally, just click on “Proceed with update” and it will start automatically.