Melt a small glob of solder onto the tip of the iron. This is called "tinning the tip" and will help with heat transfer.

You'll likely see some wispy smoke as you melt solder. This is mostly the rosin-core flux that's built into the solder wire. Flux helps molten solder flow, but gets vaporized over time. Once that happens, you'll need to either melt more solder to refresh the flux, or apply flux from an external source.

If this is your first time using a soldering iron, repeat the cleaning and melting procedure a few times to get a feel at how molten solder handles and how much solder the tip can hold.