It's unlikely you have pistons for floating pins unless you specified that when you ordered them. Most pistons are set up for press fit pins(pins are pressed to the small end of the rod but the pin does float in the piston however). If you did order floaters you will have to have your rods re-sized or rebushed for use with floating pins. Either way it's a trip to the machine shop or order another set of rods prepped for that use.
The best scenario if budget allows is to order a balanced rotating assembly: rebuilt crank that is balanced for the pistons and rods that come with the kit. The only way you can get a mail order shop like PAW or Summit to sell you pistons with the rods pressed on is to pay for custom balancing which requires the purchase of a crankshaft.
If you want to re-use your old rods with your new pistons take them to a machine shop and have them swapped out/refurbished as required. It's not allot of money and it will get done right.
If you really want to swap them out yourself you will need a shop style press and a way to heat up the small end of the rods up for re-installing with the new pistons/pins. There were some pretty good write ups on this site explaining how to do this if you check back through the archives a little.
Anytime you replace rod bolts you have to have the big end resized because the pressing in of the new rod bolt can distort the rod enough to cause bearing fit out problems. Re-sizing is a machine shop only function.