To set up your PayPal account, go to PayPal main page and click "Get Started".
Choose business account, so you can sell your photos, and click "Continue".
Enter your email address, and click "Continue". Remember to confirm your email address in an email you'll receive in a few minutes.
Select more information about your business from lists provided.
Provide holder's information and click "Continue".
Select a payment option "On your Website" and click "Continue". Then choose payments through PayPal and click "Continue".
On the next page unroll "Option A" and choose "Set up API access".
Then, choose "Request API credentials".
Next step is to choose "Request API Signature" and click "Agree and Submit".
Here you go! On this page you can see your API Username, API Password and Signature:
Now you need to copy them and go to your Photler's account settings bar "Sell your photos". Then paste them in the right sections.
In case you forget to copy your API information, log into your PayPal account and follow the same steps you did during your first set up. Move your cursor over "Tools" and choose "PayPal Business Set-up". Unroll "Option A" and choose "Set up API access" and then "View API Signature" - here you have all your API info.