Check if the junction is hot enough. Without removing the iron, begin feeding solder into the junction between the tab and the pad. If the iron is on one side of the tab, feed the solder from the other side (as depicted).
Apply a generous amount of solder to the junction. The resulting solder joint should be shiny and appear as shown. If this is not the case, lay the iron back on the pad and reflow the joint until the solder liquifies again.
Tin the tip of the iron and then return it to its stand.