Excel (spreadsheet) and Access(RAD/Database) are very different. Database is based on different concepts.
Research/Review Database Normalization, Business Rules and Data Model.
Review this short article "
stump the Model" for an overview of checking your design.
There are several articles/tutorials in various formats in the Database Planning and Design link in my signature.
See this
Data Modeling 101 by George Hepworth for insight.
Joining several sheets into one seems a start in the wrong direction, but you know your environment, requirements better than any reader.
Here's a link (via Google search) to
a payroll data model that may be helpful
And
another from M$oft (may be overkill for learning the basics)
Good luck.