Each task in Hivelight has an assignee and a reviewer position.
Both assignee and reviewer positions on a task are optional (although certainly recommended). The assignee and reviewer are also able to be the same person if you like.
You can change the assignee or reviewer for a task individually or in bulk.
Keep in mind that generally you can only assign a task to a person if they are part of the matter team that that task belongs to (the exception is if you assign tasks to a person via the workspace tasks list - this will cause them to be added to the matter team if they aren't already on it and then the task is assigned to them all in one action).
Quick edit
On the task board, click on the 'quick edit' icon on the task.
You'll then get the 'quick edit task' dialogue box where you can change the assignee or reviewer.
Detailed task view
Open the task to change the assignee or reviewer.
Scroll down and find the 'Assignment' box where you can change the assignee and reviewer.
Reassign tasks in bulk (via matter task list or workspace task list)
To reassign tasks that are all in the same matter, use the matter task list (which shows just the tasks in the current matter).
To reassign tasks that are across many matters, use the workspace task list (which lists all tasks across all matters in the workspace).
Use the check boxes to select the tasks to reassign, and then change either the assignee or reviewer for those tasks.
Important: If the user you designate as the new assignee or reviewer is not already on the matter team (for the matter that the relevant tasks belong to) this action will cause them to be added to the relevant matter team(s).