Diodes are fairly robust and have polarity, which means that the orientation matters. The stripe on the diode should match the silkscreen on the PCB, like so:
The simplest approach is to add a little bit of solder to one pad, place the diode and solder to one pad, make adjustments, and then solder the other pad.
Before moving on, audit your work. Make sure all the diodes are oriented correctly and have been completely soldered.