Help unlocking bootloader of dell venue 7 HSPA+

HEY Guys I have trouble unlocking bootloader.I installed the android SDK with no tools or no android platform.So I downloaded a adb and fastboot installer,ran it.It was successfully installed.I didn't  do anything with the android SDK I tried to run the SDK manager it force closed itself.So I fastboot my dell venue 7 and opened cmd and entered fast boot OEM devices,then it just showed waiting for devices nothingelse.I had downloaded the drivers for the tablet.I don't know what I'm doing wrong.Please help me.