How do you generate a report?

Firstly you need some data.
Reports can be generated from a table or a query.
Once you have one of those, you can create a report.

There are 2 good ways to create a report depending on your experience.

Option1
Use the Report Wizard. This is the easiest way, as Access steps you through all the steps required to create report.

Here are the steps for the report wizard.
Step 1: Source for the data - one or more tables or queries and which fields to include
Step 2: Group data on one or more fields. The Grouping Options button opens a dialog where you can choose an interval to group on, such as each month or on the first letter.
Step 3: Sort on up to 4 fields. The Summary Options button opens a dialog that offers to calculate Sum, Avg, Min, and Max for fields that are Number data type.
Step 4: Layout, one of 6 layouts. Choose Portrait or Landscape orientation for the paper.
Step 5: AutoFormat styles, one of 6 pre-installed styles.
Step 6: Title for the report, which will also be the name of the report

Option2

This is a alot more complex, and depends on many factors. You need to connect all the various pieces of the report together. Lots of detail. Once you have the Report wizard working well, you can use some of the controls on the report to modify the syle, layout, text, etc. Would not recommend building a report from scratch until you have lots of experience with the wizard and understand the controls on a report.