You can say 'You have (some)' - Εσύ έχεις or 'You have it/them/...' - Εσύ το/τα/... έχεις.
e.g. Έχεις βιβλία στο σπίτι σου; Εγώ έχω. (emphatic as in my comment above, 'some books' is implied so no object required)
Πού είναι τα βιβλία που σου έδωσα; Εσύ τα έχεις. (can't drop the object here)
You haven't seen that before? I have. ;)
However, we don't really use the verb έχω without an accompanying verb in present perfect as you can in English, like above. You just say Ναι, το έχω δει.
HOW TO GET THE GREEK KEYBOARD These links will not only show you how to get the Greek keyboard but also how to find the Greek letters on it, how to add accent
THE GREEK ALPHABET
Some simple hints to get you started: THESE ARE VERY IMPORTANT
1. Read the drop-down hints. Pass your cursor over a word and a list of words will appear. The top word/phrase is usually the best choice.
2 Always read the comments before posting.
3 Read the Tips & notes, on the first page of each lesson you’ll see TIPS Click on that.
4 Use the Report option at the bottom of the exercise page to report problems such as "My answer should be accepted." then post on the Discuss page.
If you have questions just ask.