Whether you choose to play 3-pin or 4-pin is your choice, and largely down to the area in which you are based.
There are 4-Pin leagues in Suffolk/Essex, Norfolk and Wellingborough in Northants. Also I have seen photos on the internet of it being played in Manchester and parts of London.
In the remainder of the British Isles, (including non-Wellingborough Northants ;D) 3-Pin is what we play, which would mean you wouldn't use the red peg.
You can find the Rules of Play by entering the AEBBA Website (link at top of page). This should describe where to position the Pegs and how to mark the baulk line.
3-Pin is by far the more popular variant of the game, and it is played at all levels right up to inter-County and International standard. 4-pin is just localised. For either, you should have a leather D of 8cm diameter with a white spot in the middle. You can play shots from anywhere in the D except from the 'break shot' (starting shot) when it has to be played from the spot.
Let us know where your club is, and we we add it to the AEBBA Map of all known venues in the UK ! 8-)
Should add for you, Jona, that the configuration is totally different for 4-pin and 3-pin...........
For the more difficult 4-Pin, the pegs are positioned in front of the 50 holes (whites) and the 100 hole (red), mimicking the position of the one in front of the 200 hole (black).
For the standard 3-pin, the two white pins are placed either side of - and in line with - the 100 hole, so that you can't easily play straight shots into the 30 hole. But the 100 and 50 holes are left 'free for access' - giving more opportunity for high scoring. The black peg remains in place as the main hazard.