long distance cycling

[muffin]

hi, i am a student and have recently commited to a charity cylce which is about 250k over 2 days due to take place at the end of may. i have little experiance on a bike and none long distance but i am extremely commited to this as it is for a very good cause.

any way long story short i obviously haven't a notion how to go about training for this and is there anyone out there that could set me off on the right track?

any help rrreeeeaaaaaalllly appreciated
thanks