How to set "Content-Security-Policy" for Apache and WordPress?

[hack3rcon]

Hello,
I looked at https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP for set "Content-Security-Policy". I used

Header set Content-Security-Policy "default-src 'self';"

, but my WordPress website style and graphical features are disabled. What is my wrong?

Thank you.