How should we handle Task predecessors/prerequisites

How do other people handle this within SpiraTeam?

Our sponsor wants us to plan out tasks through deployment and guesstimate an end date.  I don't see how I can do that in SpiraTeam due to the apparent inability to specify predecessors.  So, I either need to explain how SpiraTeam has been set up to do things differently or use a different project management tool for that kind of planning.  Any suggestions?  (The organization is still fairly new to Agile but I don't want to just say something about how things are done differently in Agile.  Executives still need some sense of dates so they can plan ahead.)