i cant get the sdk manager to "start"
You don't have to. Your next step is this:
6. Put your phone into USB debugging mode: Settings > Applications > Development > check USB Debugging
With a Mac, by the way, if you follow the instructions in this:
http://androidforums.com/all-things-root-eris/53963-guide-stock-1-5-latest-root-2-1-a.html
After you have that SDK folder, you only need to do these:
6. Put your phone into USB debugging mode: Settings > Applications > Development > check USB Debugging
7. Connect your phone via USB to your Mac
After you do this, your phone will ask if you want to mount the SD card. Choose not to - you want to charge only. Just connect it and do not mount the SD Card as a device to the Mac.
10. You can test to make sure everything is working by going to a command prompt, go to the \tools\ directory of the Android SDK, and type: "adb shell". If you see a "$" (or "#" if you're already rooted) sign you're good.
Ok, and explanation. You need to open the Mac application Terminal. This will open a window that has a prompt with the name of your Mac, with the folder, ending with a $.
Assuming that you moved that SDK folder to your desktop, type "cd desktop" and press return. The prompt should change to something like:
computer-name:desktop username$
From here, start typing "cd andr". Then press tab. It should fill out the rest of the folder name; press enter.
From here, type "cd tools" then return. The prompt should be
computer-name:tools username$
If so, and assuming the Eris is still attached, you can then
10. You can test to make sure everything is working by going to a command prompt, go to the \tools\ directory of the Android SDK, and type: "./adb shell". If you see a "$" (or "#" if you're already rooted) sign you're good.
You can then type "exit" and then return to get out of ADB shell mode. You are then ready to try to root.