To be able to link the task on its overview page you must have the task editing rights that are granted to full access or project administrator, project manager, task creator, task and subtask responsible persons.
Scroll down the page to the Related tasks section and click the Create new link link. If this link is disabled, it means that there are no tasks to link with or you have not enough rights to do it.
Open the Choose task drop-down list. You will see all the opened tasks assigned to the same milestone as the selected one. Select a task you wish to link with and click the OK button to the right.
The End-Start link will be created. This type of link means that the task you link with cannot begin until the task you link is completed.
The linked task will be added to the Related tasks list. In the same way you can link as many tasks within the same milestone or outside milestones as you need.
If the start date of the task you link with is set before the due date of the task you link, the created link will be highlighted in red as invalid. To make it valid you need to correct the task dates manually.
If you didn't set the start date while creating the task, the creation date will be automatically considered as a start date.
To edit or delete the created link, click the icon to the right of the link title and select the corresponding option from the drop-down list.