Different boilers have different degrees of flexibility with reset curves (some can even deliver different curves to different zones) but even with the dumbest version you use a lower outdoor temperature number than the 99% outside design temp to get it to do what you want.
The simplest reset curves are just linear with temperature- if you define it to be 180F @ -20F and 100F @ 60F or higher those would boost the temp by 1F every time the outdoor drops another degree below 60F. So at +1F it's 59F cooler than 60F, and would deliver 100F + 59F= 159F water at 1F, 160F water at 0F, 162F water at -1F, etc. Pick different numbers and end points and it'll follow a different step function, but you want the line to cross the 99% outside design temp at the minimum necessary water temp, and as low as possible above that temp.
Others will sometimes use more complex curves to compensate for nonlinearities in radiator output with bigger temperature differences, but it's still usually only two programmable points.
Many boilers offer a programmable "boost" function where it will raise the temperature by a user-defined amount it the thermostat isn't satisfied within some user defined period of time.
