Clean the inside of the a arms. Make surethey are smooth and clean. No burrs, dents, rust, ect.
Wear some welding gloves(they work great for grilling too) oil  up while hot one hole at a time. Only oil the one that you are going to press In because the oil will cool it down fast. then immediately begin pressing in the bearing. Get them as close to center as u can, using a socket that will barely fit in the arm.
I used regular motor oil. It really don't matter what kind of oil you use. Just whatever u have around. No need to get crazy picky on getting them perfectly centered side to side. Just get it as close as u can and make sure it is inside. If you use anti seize for lube, it may make the next bearing change easier, but it really don't matter. I did mine with a bench vice, socket, and I used an acetylene torch for heat. If I didn't have that I would have used the oven(when the wife wasn't there as stated above) also, if you haven't had alot of experience using a torch, use the oven cause you don't want it getting too hot.