How to take care of this plant?

Sounds good, just keep in a sunny spot.

Where do you live? Who are "they" ? This is called a Mandevilla vine they are tropical need heat year round, your variety the red one is "Aurora" https://www.nybg.org/blogs/plant-talk/2011/10/tip-of-the-week/how-to-over-winter-a-mandevilla-vine/ more https://gardeningwithcharlie.com/grow-mandevilla.html more info. http://www.costafarms.com/get-growing/news/a-shopper-s-guide-to-mandevilla Toxic Parts

Some plants have certain parts that are toxic, such as the roots or the blooms. For animals sensitive to mandevilla ingestion, keep them away from all parts of the plant. While the toxicity level is low in mandevilla, eating any part of the plant -- roots, leaves, stems and blooms -- can lead to mild indigestion.

Sap

In addition to potentially causing a few tummy troubles in your pets, the sap can irritate their skin. The sap has a milky appearance and flows whenever the vines are broken or pricked -- even pulling off a leaf can cause a bit of sap to bubble to the surface. The effects aren't severe and won't affect all pets, but if your pet already has sensitive skin, make sure he doesn't touch the plant when sap is present. The sap can soak through his fur and lead to mild itching and irritation.

Repot it into a larger pot and use POTTING soil...I recommend one with Miracle Gro fertilizer in it. You can move it in in cooler weather.

The lesson to be learn here: always know what you are buying, despite how much you might like its appearance. Enjoy it for now. Before you re-pot and bring it inside in the fall, do some research to understand the growing requirements of Mandevilla Aurora and then check what your growing Zone is like. Many vines can be kept trimmed into shape. Others need to get lanky. If it doesn't do well inside, it may be because it naturally needs long days the whole year and indoor lighting doesn't provide that. With plants - experience speaks volumes.

I LOVE mandevillas. Their cousin, diplodania, looks similar, but more like a bush than a vine. I have a PINK one that I have brought in (live in Michigan) for several years. Gets long and lanky in the brightest window I can give it. I cut it back before bring in, and trim couple times during the winter. Never blooms in the house.

Then when I take it out in the spring, it continues to grow, but is very late to bloom. And they are heavy feeders, with higher middle nor of fertilizer for blooms.

Last year I brought in a beautiful yellow and a white I had bought. Neither survived. I'm thinking they just weren't as strong plants as the Pink.

This year, I found several red ones on clearance at Lowes. Like half-price still in the spring!

I'm thinking a couple of the larger ones I may bring in. Will cut the tops back to 8-10". Put in slightly smaller pots. And put in the brightest window I can.

I really believe that the pink and hopefully red are much hardier than the yellow and the white.

But even if they don't survive, I will keep buying made villas as they are so spectacular when in bloom.

Good Luck.

Oh and don't fertilize them when inside. As they will slow way down, and won't need as much food. That said, I may fertilize one and not the other to see which is better,