Politics may be significantly impacted by how often people access Facebook news. Users' understanding and comprehension of political topics may improve as a result of being exposed to political headlines on Facebook, which may have an impact on how they feel and what they believe. Facebook users may be more inclined to have passionate opinions on political topics and engage in political activism if they often read political news on the social media platform. In this study, we examined the effects of Facebook network size, connections with public political actors, use for news, and political expression on political attitudes, protest, and participation. We did this by considering the Orientation Stimulus Reasoning Orientation Response (OSROR) framework for political engagement impacts into consideration. According to data from Hong Kong's (HK) whole population, a city that has one of the highest rates of Facebook adoption globally, structural equation analyses were carried out. Results indicated considering Facebook's size and connections to influential political leaders had an impact on users' engagement in Facebook news, expression, and effectiveness in both direct and indirect ways. Through political speech, Facebook news largely had indirect consequences. A discriminant function analysis also revealed that the most important factors for separating Facebook users from nonusers were age, education, and exposure to online news. This research has consequences for political campaigns and groups trying to enlist members on social media sites like Facebook.