With Page Layouts you can change the fields and buttons shown in a record.
A. Edit the fields shown inside the Details tab
B. Change the Related lists shown on the Related tab.
C. Change which fields appear on the top row (compact layout).
D. Change the action buttons.
More about page layouts here.
Entering the page layout editor
You must first select which object you want to edit. In this example we are going to edit Accounts.
1. Click on Setup
2. From Setup, navigate to Object Manager on top
3. Click on label Account
In the Account object’s settings:
1. Click on Page Layouts.
2. Click on an Page Layout name to edit it
Read more about navigating the Setup.
Inside the page layout editor
From here you can change what fields and buttons are shown in pages for each user.
1. The top of the editor contains the fields and actions you can use in the layout.
2. Salesforce Mobile and Lightning Experience Actions section contains the action buttons visible on the page.
3. These sections show the fields that are currently on the page layout.
! When you scroll down you can find related lists. They determine what related records are shown.
Adding fields or buttons to the page layout is done by drag and dropping:
1. Click and hold a field name.
2. Drag it inside a section and then release the mouse to drop it in the layout.
3. Click Save when done.
! Delete fields by hovering your mouse over them and then clicking the Remove icon.
More about page layouts here.