How do I seet up project to not show negative slack?

Donna,

Negative Slack will occur in situations where you have a task that has predecessors and the task itself either has a Deadline or a "Finish No Later Than" constraint applied to it.

The tasks predecessors will be forcing the task to be scheduled later than the Deadline or "Finish No Later Than" constraint date, this provokes the Negative Slack on the task.

You can avoid this situation by making sure you have no Deadlines or "Finish No Later Than" constraints applied to your schedule.

However it is unusual for projects NOT to have some kind of deadline or target completion date which is why the Deadline or "Finish No Later Than" constraints are available.

If they are valid and are applied to a schedule the resulting schedule conflict and Negative Slack will inform you as to EXACTLY how much time you need to claw back to achieve the target completion date you have in your schedule. clawing back more time than you need to may involve considerable extra cost due to in-efficient working at no addiitional benefit to the project.