How I will call or add new method or events in Standard objects in D365FO

Dear All,

Can you please let me know

A). I will add METHODS

1. New method in Standard Table.

2. New method in Standard Form 

3. New method in Standard Form DS

4. New method in Standard Form Control.

B). How I will call EVENTS in Standard(Table, Form, Form DS, Form Control) ? 

Example : 

Form> SalesTable > Event > OnActivated

Form> DS > SalesTable > OnCreated

Form Control> SalesTable_SalesTypeGrid > Event > OnValidating

Table> LedgerJournalTable > Event > OnDeleting

How I will call the above events from Standard Objects ?

Please give me more shed on this.

Thanks!