"The Online Version" doesn't help much, unfortunately...
Is it the FREE on-line version, or the PAID-FOR on-line version.
If the former, you can't really do much...if I recall correctly, you *can* build/repair (one) hut, but since it is a trial, there is only so much you can do.
If you have bought it and downloaded/installed it, then you have the full game and you can do everything I can with the version I installed from the disk (bought for $9.99).
I will work on the assumption of the latter. :D
Drop villagers onto the delapidated hut to repair it...since they don't have the skill of Building, they'll get bored, so you'll have to do it repeatedly. (Please note...if you turn the tips on, you can get all these tips for building, breeding, farming/fishing, etc.) Once one or more of your villagers has the skill for Building, you can start not paying such close attention to them. (Note: even if they have walked away from the building they are working on, they are not necessarily bored...they may be retrieving wood from the pile by the box, or stones from the area near the graveyard in the upper right.) Once you are either prompted to build a new hut, or see a rectangular area prepared near the existing hut, you can build a second hut for housing. It's been a while...but if I recall correctly, you can have two housing huts, the "Privacy" hut, the Science Hut by the table, the sewing hut, and the hospital. Most of the buildables (possibly including the second living hut) are accessed by buying increased levels of tech knowledge in the tech screen.
Also, you can increase your maximum population by researching the tech tree. (Medicine and Building if I recall correctly.)
To access the gong piece in the pool, you have to make a potion with the black flower by the grave yard (can't remember exact formulation, but the message that comes up is "You don't feel the need to breathe." You drop the person into the pool, and (s)he will dive down to retrieve the piece...just make sure you've cleared the brush in front of the gong encasement.
The box contains a second piece of the gong, and requires two or three Master Builders to disassemble. (Others can help, but you NEED the Master Builders to do it.)
PS: If you want all the potions, type in a question to Google and you'll find dozens of sites that can/will give you the potion formulas for free...and complete walkthroughs if you want them.