[shinee]

and then just push them back on the bottom after I took out the device?

The reseal must be an exact representation of the original packaging.

also just fill it up with anything that weighs enough correct?

Of equal weight (or close to It), preferably with a like-for-like dummy product.

I do not have sopmething like a dummy so I fill just fill it up with something else.
I hope the opened seal can be reattached to bottom easily without any sign of tampering