Hi Missy, welcome to the site
There's been quite a few posts about starting at this time of year, might be worth you browsing for them in the Welcome board as well as this one, but I can point you in the right direction!
First, look at the advice on clearing a plot.
http://www.allotment-garden.org/articles/Clearing_a_New_Allotment.phpAlso, look at the advice on planning a plot.
http://www.allotment-garden.org/articles/Planning_the_Plot.phpWhilst also having a look at what to sow / harvest and when.
http://www.allotment-garden.org/vegetable/general/sowing-harvest-vegetable-chart.phpYou don't say what sort of condition your plot is. Essentially, make sure you get as much of the top foliage down as possible and then start to tackle it.
In tackling it, you may choose to be organic or not. There are pro's and con's for each approach, and other threads recently have comprehensively covered these.
However you do tackle it, I'd suggest doing a bit at a time, and aim to get something in as you go along - gives you motivation and you can see progress.
Whatever you have not covered, make sure you keep under control. Either by covering it (not carpet, alternatives include weed fabric, plastic - though not for any length of time - and cardboard). Otherwise the weeds will come back and you will lose heart.
This thread gives you an idea of what others might be planning to get in soon - leave it much later and you're probably looking at other types of veggies which overwinter rather than summer crop.
I'd suggest you put your location in your profile, as it makes it much easier to tailor any future answers accurately.
And Good luck!