Calculated Fields are as easy to add as any Field in your database. If you are comfortable creating fields and adding them to your layout, you may proceed. If not, now is a good time to consider "outsourcing". (In other words, call me to do it for you. I recently created 85 fields in a database and added them to the database layout, in a tab that I also created at that time, in under 2 hours. If this is not something you do often, there can be significant value in paying me to do it for you.)
So if you are comfortable creating fields and adding them to your layout, here is the "cheat sheet": First you create the Field as a Calculated Field, then you add it to your Layout. (Adding Fields to your Layout will have to be a future article, but some layout issues are in my blog.)
To add a Field, you simply select Tools, Define Fields, Create New Field, and then choose your new Field's characteristics.
Here is where some people experienced in adding fields get "tripped up": When you name the new field and then select the Field Data Type, the list defaults to "Character" on an alpha list, and the Calculated selection is above that, out of view (as shown below). Select the list so you can scroll UP to Calculated, then select Calculated.
A few more helpful tips:
1. You cannot edit an existing field to make it a calculated field: You must create a new field, and create it as a calculated field.
2. A calculated field can be a Decimal, a Number, or Currency. Dates can be included in the equation of a calculated field (i.e. it can calculate the date "90 days before" a specific date.)
3. A calculated field will not calculate a formula when an included field is empty: You must populate all fields in the equation. This can easily be done by looking up all records wherein an included field "does not contain data", and using the Replace Field function to populate the empty fields. (Here is how to replace the contents of a field in multiple records.)
4. The calculated field does not necessarily show up immediately: You may need to "force save" or move off the record then back to see the completed calculation.
Calculated fields can add value to your database in a number of ways and I can think of many, many examples. If you want to discuss it more, please contact me.