How to get play store on samsung galaxy gt s520 !

Samsung Galaxy S3 Pebble Blue, boxed unwanted upgrade
hi there, i have a brand new and boxed samsung Galaxy s3 for sale. Pebble blue and has not been used at all. still boxed with all the p[lastic coverings. would have loved to keep myself but only just beginning to get used to smartphones! Only prepared to sell within the uk, preferably local sale. postage shall have to be paid for by the buyer. contact me for any info required. thnx