Simone - you shouldn't need any tools. There's a tube inside the tire, and your tube is bad.
You can buy the tubes with the "green slime" inside of them for about a buck more than a regular tube, and the slime should seal any new holes that develop during cycling.
1. you take the tire off, it should slip off around the sides
2. Remove the tube, take your new tube, and lay it inside the tire (assuming your tire is still with the treaded side of life) - making certain that the Schraeder valve is poking through the proper hole (you know, the little valve stem thingo that you air up the tire with?)
3. slide the tube n' tire combo back around the wheel making certain that the valve stem pokes through the inner portion of the wheel/rim as it should.
4. air up tube and tire to specifications.
5. all this is slightly more complicated on the rear tire, as that . . . .can be lots more difficult depending on make and model.
. . . . .hopes to have helped. The "green slime" tube advice was the only decent info that maybe you didn't know.
. . . .wish I could just do it for ya.