Phil & Walrus have mostly got you covered, what I would recommend is before you remove them, put the jack under the lower arm, remove both top & bottom BJ nuts, clean & oil the threads & put the nuts back on by hand until you contact the nyloc part of the nut before trying to extract the BJ's from their tapers. Also, mark the upper arms L & R, & pay special attention to where the shims go.

You can get the arms off the car with just a hammer, but you need a press to push the new BJ's in.