You're right, they are all linked. I think they are part of the same dot point (too lazy to go check) which would mean you would only get a question that involved all of them. Just briefly:
- RECRUITMENT involves governmental attempts and methods to recruit more troops (I know, very insightful description. Sorry but I can't think of a better way to put it). This also needs a comment on conscription. Recruitment was the main goal behind censorship and propaganda.
-CENSORSHIP involves the various governments' approaches to censoring material regarding the war. Germany was especially stringent when it came to censorship, check your text book for a more detailed explanation of why this was an what it involved. Often letters from the Western front were censored in order to prevent the homefront from losing morale. Also journalism was severely reigned in, articles often the result of bribery in an attempt to avoid the publication of anti-war material.
-PROPAGANDA is essentially the reverse of censorship. You should talk about the different methods (Britain's cinema short footage of the Somme, posters, newspaper articles), and the target audiences of propaganda. For example some propaganda specifically targeted women, because it was believed that women had the potential to significantly influence the recruitment process. Propaganda sometimes attempted to portray the war and the war effort as an adventurous, patriotic stance, while at other times it used guilt to persuade citizens to 'do their bit'. A good example of this is the famous poster "What did you do in the great war Daddy?"
The way I see it is recruitment = the aim of censorship and propaganda, which were the methods governments used to achieve recruitment. However, there were also other reasons behind the implementation of propaganda (eg to maintain momentum behind the war effort at home) and censorship (eg to cap anti-war protest).
Hope this helps!