If you want to add a new Tab in Company and Contact create/update window and want to show those tabs in details section then you have to create new content type. Here I will give you an example of how to add new tab (content type) in company list. Follow the following steps to create new content type.
You can add any content type from the list. Select a content type from “Available Site Content Types”, click on add > button then you will see the selected site content type in “Content Type to Add” section. You can filter content type list by changing the “Select site content type from” drop down list.
Click on OK button. Now you can see the newly added content type in the content type list.
It will show you Content type settings page. By clicking on the Name and description page you can change the name of the tab (Content Type)
You can change columns too by clicking on the columns.
You can add more column in the content type by clicking on the “Add from existing site or list columns”.
You can change the order of the column by clicking on the Columns order link.
Now you can see the new tab added in Create form. You can also change the tab order.
Lets add newly created tab in index number 3. So choose 3 from the position dropdown list. Click OK button. Now open company create window to see the changes.
[Note: If you can’t see the change please refresh the page.]