How to connect paypal

I want to know ;
The way that connect both online and offline payment plugins to add property and
the way that connect paypal for addproperty

Hi,
if you integrate your OS Property with membership pro component. User must pay before upload the property. If not, agent only pay for you when they want to upgrade the normal property to featured property. And we accept paypal payment gateway for this case.
Thanks
Dam

I want to integrate paypal with addproperty feature of the osproperty component. Here i don;t need membership plans. and just need only ,when front end user is filling the addproperty form and there after it should display the paypal interface with predefined amount just like shopping cart system. Here payment page should be prompted just after filled the form by the user. I attached a photo like that i need to be required

How to do this.