Hi Kelly, congrats on getting an allotment. It does appear daunting when you're faced with a large expanse of wilderness.
What worked for me was looking at it as an ongoing project. First step was to cultivate enough just to grow a few basic crops in the first year. The rest of the plot can be covered in plastic, old carpet etc or just kept under control with a strimmer.
Gradually you can increase the area under cultivation, having fruit beds helps, as once planted you don't need to do any further digging, just weeding and mulching.
Give yourself manageable chunks to do, otherwise it becomes a chore. After all it should be fun.