Here are the steps for turning on "Accept remote API calls" in your JIRA system:

1. Log in to your JIRA system as a user with the JIRA Administrators global permission.
2. Go to Administration > System
3. In the resulting page, click the Edit Settings button at the top of the page.
4. Scroll to the "Options" section, and look for the "Accept remote API calls" option.
5. Click the "On" radio button
6. Then scroll to the bottom of the page and click the Update button.