You can create powerful Access databases with no programming code at all. There may be a situation though when you do need some specialized functionality and then you will have to create a VBA Access database.
The programming language used in all the MS Office products is VBA which stands for Visual Basic for Applications.
How do we go about this? It really depends on the type of functionality you require, but chances are you will find yourself creating sub procedures and functions. This will hold the main code of your program. Code can be put behind the forms itself or in code modules.
There is a bit of a learning curve however when it comes to creating a VBA Access database. It takes time to become confident and proficient in a programming language.
You can also get proficient in the MS Access macro language which will give you a start in how logical statements flow. MS Access macros are essentially VBA Access statements, but are much easier to use.
If you feel confident to attempt a VBA Access database then you should, otherwise enrol in a good training course. There are also plenty of good books on the MS Access VBA language.