instead of paying for a shop or using a hammer and potentially damaging your bearings you can make an easy homemade press
you will need
threaded rod (i used an old 3/8 mtb axle)
nuts that fit on the threaded rod axle etc
2 huge washers
put the washers on and then the nuts, and it should look something like this:
to use take off one of the nuts and that washer, put bearings in bottom bracket along with tube spacer, put it through, bu the washer and nut back on and tighten one side stoppingthe other from spinning by using a wrench
and there you go!