Hello and Welcome someone with more experience should be on soon. Have any question? A run down of your enclosure or a picture would help someone to give better info.
Welcome, and congrats on your new tortoise! Greek tortoises are so much fun... we have one little Greek, and 4 RTs (in separate enclosures).
The pic didn't attach... there are good instructions on how to do that HERE.
Caring for a Greek tortoise is almost identical to caring for Russian tortoises (except the 2 different species shouldn't be kept together). You can find a wonderful comprehensive caresheet at www.russiantortoise.net and there is also a good list of edible plants on there. If you are interested in learning more about which 'wild' plants (in non-sprayed areas) or garden plants are edible for tortoises, there is also a really nice list HERE that is printable and has photographs.
I started out just feeding a few plants I already knew were safe, and bit by bit expanded what I fed from my garden - daylily leaves and flowers, raspberry leaves, mallow leaves, mullberry leaves, fig leaves, dandelion, plantain weed, and so much more!
We'd love to hear what you are housing your tortoise in, what kind of substrate you are using, and what your temperatures are like, what kind of lighting, etc. - not because we are nosy, but because often pet stores will give faulty info... I find that folks on here are generally really nice, and if something needs to be corrected, will be kind about mentioning it.