In order to merge applicants into one application, you will want to make sure both applicants have completed their application forms. If one person has not yet applied, you can simply add them as a roommate to the existing application and invite them to fill out the online application form. 

First, you will want to navigate to the property's dashboard in CRM. You will then click the "Traffic" tab and then "Group Applications". 

Once you are in "Group Applications", you can then search for the primary applicant. In this case, it doesn't really matter who you pick to be the primary so simply search for one of the two applicants and click "select". If you are grouping two prospects who are in different stages of the leasing process, you will want to make the primary whoever is further along.

After you have selected the primary applicant. You will then be given the option to "Add Occupants/Applications", click this option. 

Search for the other applicant and click "Add to Group"

You have successfully grouped the applications and can now proceed to screening. If the applicants were screened prior to grouping them together, it is standard practice to rescreen the applicants as a group.