Kids Drum Set, Beginner-Friendly, Metallic Finish, Natural

The pieces of hardware that hold the metal stems of the snare/cymbal/etc. have come very loose. Is there any way to tighten them?

Yes. You can tighten them by turning the knobs or nuts where the stems connect to the base. If they still feel loose, check for missing washers or worn threads and replace those parts if needed.

how do you put it together

First, check the contents of the package and make sure you have everything you need.
Next, set up the seat by attaching the legs and the cushion.
Then, set up the bass drum by attaching the drum head, the hoop, the bolts, and the spurs.
After that, set up the cymbal holder and the tom/snare drum holder on the bass drum.
Next, set up the cymbal, the tom drum, and the snare drum by placing them on the holders and adjusting the angles.
Finally, set up the pedal on the bass drum hoop and connect it to the bass drum.

You can also use the drum mute mats to reduce the noise level of the drums