To assign the same Project to multiple users at a time
- Go to the Assignment tab in Salesforce
- Click the New Assignment button
- In the New Assignment pop up, select the Start Date and Time and the End Date and Time
- Select the Project from the Project list
- Select the users from the Assign to Users drop down and
- Click the Submit button
- Now the Project is assigned to multiple users (the users that you selected in the Assign to User field).