Hi everyone!

I recently picked up my first bonsai tree at a local nursery. I'm not sure how to care for this tree because I don't know what it is. I have tried the tree identification tool on this site, but nothing quite seems to match.

The person at the nursery said it was an elm. But all of the elm trees I've seen online have toothed leaves, whereas my tree's leaves are smooth. There appear to be some small air roots forming 1/2" above the soil, which made me suspect it was some kind of ficus. But per the identification tool, fici have alternating leaves, whereas this tree appears to have opposite leaves.

Appreciate any thoughts you might have, especially concerning how I can care for this tree indoors (I live in an apartment with ample morning sunlight, but no patio or balcony available). Thanks!

Is this a Serissa? It does resemble the photo on the Serissa species page, but it looks very different from the example shown on the "Identify my Bonsai" page. I attached the photos -- both of these are labeled as Serissa, but they look completely different to my eyes. One plant has thin, long, light leaves, where the other plant has short, thick, darker leaves with a yellow outline on them. Are these different species?

Yes, I would also say serissa.
Serissa is the family name. There are several species in the family. Serissa Foetida (The smelling serissa) is one used often in Bonsai, and seems to have several varieties, one with and one without white edges.

That is however where my understanding of serissa ends, because I try to avoid plants that you have to bring indoors for winter.