You can create dependencies from both the table and timeline portions of the Gantt chart.
Tasks with deffered or cancelled status can't be a part of a dependency. Completed tasks can only be added as predecessors.
Locate a task in the table and double-click the Predecessors column. If you don't see the column, click the gear icon in the table's upper left-hand corner and check the box next to Predecessors.
Find the task that should precede the task from Step 1.
In the task from Step 1, enter the row number from Step 2's task followed by:
FS – to create a Finish to Start dependency
SS – to create a Start to Start dependency
FF – to create a Finish to Finish dependency
SF – to create a Start to Finish dependency
Press Enter on your keyboard.
If you only enter a number, then a Finish to Start dependency is created by default.