Activities that make up a model can have master data such as roles, systems, locations, etc allocated to them. 

In the properties inspector for an activity, under the Details section, you will see the RACI roles (Responsible, Consulted and Informed. Accountable roles are shown in each swim-lane). 

To add who is responsible for an activity, click the edit list button. Here you will be able to choose who is responsible for this activity. You can also select multiple roles if need be.

Once the changes have been saved, the role will be displayed next to the activity.

Once all master data has been added, the outcome may be similar to this.

To add a new piece of master data, this will need to be requested for it to be successfully added. When editing the role, click on the Add New option.

Here, you can add the new role as a local resource or you can request for it to be added as master data. If you're adding it as a local resource, this will be added immediately. For master data, this will be sent as a request to the author of the master data file which needs to be approved.