All wires are connected but i have no power to my amp.
For the lowest resistance connection, your ground wire needs to be in good solid contact with bare metal of the vehicle frame or body within about 18-24" from the amp. The ground is probably the most important connection you'll make to the amp. A bad one will not only rob your amp of the current it needs for best performance, it could result in damage to the amp or the vehicle itself. The ground should be the FIRST connection you make, and you should spend some time making sure that it is a good one. At the absolute minimum, you should test the "resistance" between the negative battery terminal and your intended ground point. Anything above about 5 ohms and you should look for a better ground. 2-4 ohms is OK, but you'll lose some input current and that means less output. I like my meter to read 1 ohm or less, before I'm really happy with the ground connection.
You may need to pull back plastic panels and/or carpeting to get to the metal. Then, find an existing bolt or screw that goes into or through the metal (a seat bolt is good, and most trunk, hood, and many dash screws go into metal). If you are unable to find an existing screw or bolt, you can drill a hole and attach the ground with a new "self-tapping" sheet metal screw. If you do decide to drill, use a drill stop and be VERY careful around any lines or hoses. Use sandpaper or a small Dremel grinder to remove any paint, undercoating, or soundproofing materials from around the hole. Crimp the ground wire to a "ring" terminal and put a toothed lockwasher under the terminal. Make sure that the head of your screw is sized to completely surround the ring terminal and tighten it until the lockwasher bites slightly into the metal. DO NOT overtighten, or it will strip and come loose. If you wish, you can cover it with dielectric grease (like mechanics use on battery terminals) or you can seal around it with silicone. You can also spray-paint it with a corrosion resistant paint. Rust Oleum flat black works well.
Hope this helps.