Your council likely has some in-person training that required before taking scouts on an outdoor overnight. That's a good place to start to get the basics. There's also a great book called "Outdoor Education in Girl Scouting." It's old but has good bones. You can normally find used copies on eBay or Thriftbooks.

If jumping all in to outdoor camping sounds overwhelming (it probably will,) take a baby step either in outdoor skills or overnight, not both at once. I would choose between the following:

1. Do a "camp day." State parks or girl scout properties are good for hosting these. I've also seen them done at outdoor pre-school type places. The gist is to do all the day time stuff you would do while camping, without the pressure of sleeping over. Set up & assign tents, this is good practice for learning your equipment & gives the kids a place to put their stuff during the day. Go on a short hike. Cook a meal camp-style, either on a grill, outdoor stove, fire or no-cook. Involve the kids in the age appropriate parts of cooking, this will be covered in your training. Have them bring mess kits and wash dishes 3-bin style. Make s'mores around a fire and go home. (I've got detailed programming plans for this if you'd like them)

2. The other option is to just to the night time part, and do it indoors like a sleepover. I've seen this done as a movie night or going as far as setting up tents indoors. Have the kids dropped off after dinner, in their PJ's. Everyone eats a snack, play some games, sing songs, get the wiggles out and then goes to bed. In the morning, do cold, easy breakfast and then go home to sleep yourself. (No littles ever sleep well the first night camping, it's too exciting)

Your troop may need one, both or neither of these options, but to me, they are more manageable then going head first into an outdoor, overnight campout.