I lost my apple tv remote. How can i turn on home sharing on the apple tv without the remote so that I can use the REMOTE app?

To the best of my knowledge, you can't. You'll probably need to buy a new remote unless you can borrow one somewhere. I believe this one is correct:

http://store.apple.com/us/product/MC377LL/A/apple-remote?fnode=61

but you'll want to confirm with Apple.

Regards.

It will work with any Apple remote, not just the swanky, but expensive silver one. You can pick up a whit one off ebay very cheaply.