So, you want to have that greeny "online" badge near your IGN on search results page.

There are three options, actually.

1. Be on ladder. This is hard but achievable. (You have to be on the character who's on the ladder to be shown as online).

2. DEPRECATED Every hour whisper poexyzis with any message. This works for all leagues.

3. Go here. Send any message. Wait for a reply. You'll know what to do.