Before installing the basin put the wast fitting in first and put a little silicone sealant around the joints and don't overtighten, (just over hand tight), the small threaded hole should face the back of the basin. Clean off any excess silicone thoroughly now as you won't get it off when it's cured later. Fit the tap so its nice and tight and does'nt spin and then fit the basin to the wall.
pipe up the taps and waste just being mindfull of where the pop up gubbins will be situated, so if you can keep the supply pipes well back and out of the way of the mechanism the better, also with the waste, a straight through vertical trap and take the waste away as low as possible would help.
Then comes the rods, insert the rod through the tap first and then the one into the waste, (which should have the entry hole pointing toward the back of the basin), cut this to length if necessary to allow it to go in.
The way these usually fit together is a cup shaped plastic washer on the short end of the shaft, (the ballend), that takes the shape of the ball, and then the same type of washer on the other end of the shaft followed by the small round threaded knurled nut which fits on the waste fitting and tightens according to how stiff you want the popup to be. (depends on what type of fitting you have).
Next slide the transmission piece, (the bit that connects the two shafts together), up the piece that is coming from the tap end and then manipulate it onto the piece coming out of the waste.
If you can't get to one of the screws for tightening try turning it around so that both screws are accesable.
Pull the rod coming from the waste down, (this will be the popped up position), and put the shaft coming from the tap in the position desired when the popup is in the up position, (pushed down letting water out of the basin), and tighten up the two screws on the trasmission piece.
Alter the screw and the locking nut on the base of the plug and operate so that in the open position, (pushed down), the waste is high enough to let the water out at a reasonable rate and in the closed position, Pulled up), low enough to create a good enough seal to retain water in the bowl.
if you need to trim the rods after, mark them up with a marker so that you don't cut htem too short if you disassemble them.
Finally tighten the knurled nut on the waste fitting according to how stiff you require the waste to operate.
Hope this helps, Regards, Trev....