You need to first create users at https://cp.hostallapps.com. Once you have created the users in the Control Panel; then you need to follow the steps given below to give permissions in your Project Server instance.
1. Login to the Project server site with the site collection administrator.
2. In the settings section click on Server Settings.
3. Click on Manage Users under security section.
4. Please fill the appropriate details and make sure that User Logon Account field in user authentication section is the SAM account name of the user.
NOTE: The SAM Account name can be located in the Control Panel under the specific user. You need to scroll to the bottom of the page to locate the SAM Account name. The SAM account name will always start with “HOSTALLAPPS\”….For example HOSTALLAPPS\john_smith.
5. Give the appropriate permissions in the security groups and global permissions category.