As has already been stated, yes, it's just easier to install with the crankarm off. If the crankarm is really seized on there, a good quality crank puller is probably necessary. I suggested the self-extracting bolts as I have found them very handy for solving severe chainsuck issues out on the trail with just a 6mm hex, and it eliminates the need for a socket wrench to tighten them. My actual reccommendation would be to invest in a proper crank removal tool, and then consider something like the self-extracting bolts for convenience. The cost for either with some frugal shopping should be under $10.