I am assuming control arm bushing right? The giant rubber bushing with metal inner-collar? I have one on a Mercedes but several on BMW and SAAB. The hard part is getting the control arm off, you've already done this....so pull the new bushing out wherever it is right now and then.....listen...make sure you have the bushing facing the correct way...if you look at the sides of German bushings there are little arrows to indicate which side they go on....next..get this special gel from MB (regular folks use slightly diluted dishwashing liquid) and lubricate the bushing entirely...then press the bushing into the arm entirely and quickly...the lubricant should work....then you re-install the new bushed control back into the car....here is the pre-loading part...don't fully torque the bolt/nut on the control arm bushing, tighten lightly and then put the tire back on, then lower the car slowly off the jack and let the new bearing load itself, that's why you have lubricate the bushing...it facilitates both installation and pre-loading but you gotta move quick