Just bourght leopard gecko!! help!!?

i have jut bourght a leopard gecko and put her in my 20 gal woodern viv, but i think shes only young reptile cymru (shop i bourght her from) didnt say how old but i thinks shes less than 8 months but i have had her for 2 days and she isnt feeding well hes had 1 cricket and because she new and shes my first gecko i have only ever had snakes, i dont no how to introduce her to her crickets and i dont no the best way of feeding her ??? and i dont no how many??? its really hard to transfer crickets from one box then i hvae been waving themin front ovher but she dossent want any??? any help or tips plz!!!!