The first place to turn for further info is Fide.com, where under 'Handbook : D. Regulations for Specific Competitions', we find D.I. Cycle for the Individual World Championship. The first six chapters are
01. World Championship General Provision
02. Zonal Tournament
03. Regulations for the World Chess Cup 2015
04. Rules & Regulations for the FIDE World Championship Match (FWCM) 2014
05. Rules & Regulations for the Candidates Tournament of the FIDE World Championship cycle 2012-2014
06. Regulations for the Grand Prix
That first chapter, 01. World Championship General Provision, starts, 'The World Championship Cycle consists of the following events:'
A. National Championships which are the responsibility of the member-federations of FIDE. The national federations retain all rights in their internal competitions.
B. Zonal Tournaments which can be organized by the Continents according to their regulations which have to be approved by the FIDE Presidential Board.
C. Continental Chess Championships: The Continents, through their respective Boards and in co-operation with FIDE, shall organise Continental Chess Championships. The regulations for these events have to be approved by the FIDE Presidential Board if they are part of the qualification system of the World Chess Championship cycle. The Chief Arbiter and the Appeals Committee of Continental Championships are nominated by the FIDE President.
D. FIDE World Cup: organized in accordance with the published regulations on the FIDE website (link).
There are further paragraphs for E. FIDE Grand-Prix, F. FIDE Candidates Tournament, and G. FIDE World Championship Match, which I'll ignore for now, because they are later in the cycle. The 'General Provision' document also lists the member countries of FIDE (177 of them at this time), split into 'zones' along with a number of qualifying places per zone.
Those qualifying places aren't explained. You just have to know that they relate to the number of places available for the FIDE World Cup. The roles of National Championships, Zonal Tournaments, and Continental Championships are explained in the 'Regulations for the World Chess Cup':-
2. Qualifying Events for World Cup 2015
2.1. National Chess Championships [as above]
2.2. Zonal Tournaments [ditto]
2.3. Continental Chess Championships [ditto, then the following]
2.3.1. FIDE shall guarantee a minimum grant of USD 92,000 towards the total prize fund for Continental Championships [...]
2.3.2. Where a Continent decides to have zonal tournaments [...]
2.3.3. All the Zonal qualifiers, as well as the number of players eligible by country to participate in each zonal, can participate in their Continental Championship [...]
2.3.4. Continents must have organised at least one Continental Championship [...]
2.3.5. The number of qualifiers for each continent is: Europe 46, Americas 20, Asia 20, Africa 6.
This is all a little confusing, but at least you know that your qualification depends on the continent where you live. The regulations for each continent are available on other web sites. Those sites are linked from FIDE's page on the Presidential Board (PB), because the four Continental Presidents are members of the PB.
I'll look at the continental regulations in part II.