Hi Chhabilal,
Go to your WordPress dashboard and click Appearance then Menus. Click create a new menu at the top and give it a name like Main Menu. Then save it.
On the left side you can add different types of items. You can add pages categories or custom links. Just select what you want and click Add to Menu button.
To change the order of your items just drag them up or down. If you want a sub menu then drag the item slightly to the right. This creates a parent child relationship.
Scroll down to the bottom and find the display location section. Check the box where you want your menu to appear then click Save Menu again.
If you use WordPress 6.0 or newer you might see Navigation Block instead. In that case edit any page and add the Navigation block from the block editor then add your links there.
You can read more details here:
If something does not work please tell me which step you are stuck on and I will help you.
