For the selected task, Predecessors and Successors can be found in Task Properties>Links.
Task Properties can be opened from the Windows tab.
Additionally, you can add the Predecessors or Predecessor Details columns to the Task list by right clicking in the Task table header and choosing Customise Columns. Predecessors column list the Task IDs of the Predecessor Tasks, while Predecessor Details list the Task ID, link type (eg. FS) and Lag if any.