You are hardly alone in killing your first bonsai. Most, if not all, of the people here killed their first one. The Learning curve is steep at first.
Determining species is the first step in caring for a bonsai. Indoor trees aren't really. There are not species of plants or trees that 'like' to be grown indoors. There are only those species that can tolerate the harsh indoor conditions (extremely low light and humidity, no air circulation, etc.). Ficus, schefflera and a couple of others can handle it, mostly. Junipers, maples, elms (even Chinese elms) don't.
Your location (state, etc. ) has a huge impact on how and what kinds of trees you can grow. Putting that info in your avatar on the left helps everyone here give you the best advice.
Watering is the second big step in learning how to keep bonsai. It's critical (and complicated by the crappy soil used in big box store and mass produced 'beginner' trees).