How to i add a contact to compaign?

I created compaign and added a web form to it (https://i.paste.pics/5OU04.png). And I want that the users who submitted the form were added to this compaign. But they are added to the general contact list (https://i.paste.pics/5OU10.png), but not in the compaign (https://i.paste.pics/5OU0I.png).

How can I set this up?

You have nothing in there for them to remain being an ‘active’ contact, that’s why your ‘active contacts’ show as “0”.
The second they fill out the form, there is nowhere to go, so they are no longer ‘active’ in the campaign.

Put a sequence behind the form that has a 3 month delay timer inside of it.

That will ‘hold’ the person inside that campaign for 3 months and show them as ‘active’ in your campaign.

In the same way you use tags to start campaigns, when the webform is submitted it acts like a goal that is triggered and can be used to start the campaign.

Or you could raise a tag when the webform is submitted and then use that tag to start the contact through the campaign.

Either approach works.