To use prestashop api following things should be done:
1. Enable prestashop webservie : Go at Advance Parameters > Webservice and enable prestashop webservice.
2. Add a key: After enabling the webservice add a key and select the resource which you want and give the desired permission to that resource.
The endpoint to your store's webservice is located in the
/api/ folder at the root of your installation of Prestashop:
To access it, you need to provide your API key when request. There is no password, providing your API key is enough – and therefore the key should be kept secret by the user!
You can either type the API endpoint address directly then enter your API key, or indicate your API key in the address. Here is an example, with "UCCLLQ9N2ARSHWCXLT74KUKSSK34BFKX" being the API key.
For more help you can view the prestashop webservice documentation.