For manually adding reviewers using their E-mail or name, hit enter on your keyboard or click the [+] icon to select their editing or viewing privileges.
If you are adding more than 2 reviewers, you can use following methods to do so:
1. Adding Reviewers on the Same Approval Line
For adding reviewers in the same approval line, press + button at the same step and enter two different reviewers. This means that these two go through horizontal approval process.
2. Adding Reviewers on a New Line
If you click the [+] icon as you can see in the second example, you add the second tier of reviewers. These reviewers can only begin their process once the first line of reviewers approve the document.