Answer: It sounds like you have a tomato well suited to container growing. Your plants will grow best if they are not crowded together, so you will need to remove all but the strongest seedling. (You can transplant the others to their own pots.) When the plant's roots fill the pot, you will need to move it into a larger pot, and then possibly eventually to a very large pot.
Tomatoes do best in a rich soil with ample water and full sun, so your plant will do best with the maximum amount of light available, either a very sunny south window or under flurescent ligh, until it is warm enough to set it outside.
You will need to harden it off or acclimate it gradually to being outside in the wind and weather. Tomatoes hate cold weather, so be sure not to let it get frosted. This may mean setting it outside for the day and bringing it in or covering it up at night until the weather settles. A rule of thumb is not to leave or plant tomatoes outside until nights are reliably in the 40's.
Enjoy your plant!
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