Add this code to your .htaccess file:
<IfModule mod_headers.c>
# Enforce HTTPS
Header always set Strict-Transport-Security "max-age=31536000; includeSubDomains; preload"
# Content Security Policy
Header always set Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline';"
# Prevent Clickjacking
Header always set X-Frame-Options "SAMEORIGIN"
# Prevent MIME Sniffing
Header always set X-Content-Type-Options "nosniff"
# Referrer Policy
Header always set Referrer-Policy "strict-origin-when-cross-origin"
# Permissions Policy
Header always set Permissions-Policy "geolocation=(), microphone=(), camera=()"
# Cross-Origin Headers
Header always set Cross-Origin-Embedder-Policy "unsafe-none"
Header always set Cross-Origin-Opener-Policy "same-origin-allow-popups"
Header always set Cross-Origin-Resource-Policy "cross-origin"
</IfModule>