Ofcourse you need to be admin of your page. Go to the page for which you want to send message or an update. On the left panel (Just below your page’s display picture) click Edit Page. After that, click Marketing on the left panel and then click Send an update. On the next page, write your message and click Send. That’s it
You want to send a message or an update to all of your Facebook fan page. What will you do? I f you have 1000’s of fans then it seems impossible to send message one by one to all of your fans. Well you can send one message to all of your page’s fans. Here is the tutorial.