You don't need to do anything; you'll automatically be set as inactive after a certain amount of time since you've last been awarded points. On your end, you'll still be able to log in and do everything you could before; you just will be grey in the full member list and won't be counted in the multiplier. And, when you've got more time for HOL, just earn points to be active.
Hope that helps.
*steps off the Headmaster's toes*
"...they didn't think there was anything very odd in anyone being a little odd."
-James Hilton's Random Harvest