Before getting Apache logs (access logs, error logs, etc.) into Graylog, you will want to configure Apache to log in a format Graylog can parse, like GELF or JSON.
One way to collect logs from a Windows or Linux system is use a log collector, like filebeat. This collector is built to collect log files and ship them to a central location. You can then use Graylog Sidecar to manage your log collectors.
((Additionally, you could create a custom shell script that sends JSON-formatted logs directly to the Graylog server using TCP.))
The Apache Web Server content pack for Illuminate will parse and configure Apache2 logs for Apache HTTP Server on a Linux system. It supports two access log formats: common and combined logs.