Step 1: Go to the BlogVault website and sign in using your email ID. 

Step 2: On the BlogVault site listing page, select the website in which you want to perform this operation.

Step 3: It'll take you to the Site Detail page. In this page, find the Themes card. Here you can click on Manage Themes.

Step 4: Click on the drop-down to filter the themes to only the ones requiring updates.

Step 5: Pick the themes you want to update and click the Update button which you can see on the top right of the screen.

Step 6: One popup window will appear on the screen. Here you can enable Visual Regression and also take a new backup before performing this operation. Click on Proceed.The selected themes will be updated by BlogVault.