Hello,
Based on your screenshot, It looks like you "INFORMATION" form has 5 tabs.
1. General
2. Features
3. Notes
4. Corporate Communications
5. Administration
These tabs may have some Sections, Fields and Subgrids.
All the other tables which has connection with your table shown in screenshot will be shown under common and in front view of Form these tables will be shown under related tab as shown below:

If you want any other subgrid in the tab which is shown already. For e.g. adding contact subgrid in details tab, please follow the below process.
1. Add a section in the tab and then select on subgrid on top ribbon bar

2. Add the related subgrid as shown

Hope this will help you. Write back if anything else is needed.
If you find this helpful, please mark it verified.