Say you have a character that you want to convert to ICONS from another superhero roleplaying game system. You may be thinking, "wouldn't it be nice if there was some conversion document available to make this process easier?" You want to know how do the traits in one game relate and compare to the traits found in ICONS, and what the "formula" is so you can convert your character over as accurately as you can. My advice?
ICONS Character Folio software, that I have found this to be the best approach when doing conversions. Now take your description or list and start crafting your character from the ground up in ICONS - use the optional "point buy" system (or don't, sometimes not limiting yourself to a static 45 points can be liberating and allow your creativity to flow, but try to keep it reasonable while giving yourself permission to use whatever number of points you feel you need). In addition to the abilities, specialties and powers, don't forget to make use of aspects, both qualities and challenges, and feel free to use these narrative devices inspired by FATE to model your character even for details that might be more quantitatively defined in more traditional roleplaying systems. If you need them, this list of benchmarks at the ICONS Truth, Justice and Gaming Wiki provides some examples featuring Marvel and DC Comics characters.
Marvel Super Heroes RPG from TSR (a.k.a. MSH or FASERIP), for example, converts quite nicely into ICONS as it was one of the game's inspirations, like FATE. The ability scores in both games have a 1 to 10 range (as well as named range levels) and map nicely to one another: MSH's Fighting, Agility, Strength, Reason, Intuition and Psyche become in ICONS Prowess, Coordination, Strength, Intellect, Awareness and Willpower. MSH's Endurance is gone but that's handled to an extent in ICONS by Stamina and other rules. See the benchmarks linked in the paragraph above for more thoughts on converting from MSH to ICONS too.
Additionally, Jason Sunday offered these suggestions for Mutants and Masterminds Second Edition to ICONS conversions back when ICONS first came out in 2010 and are worth taking a look at.
This advice comes not just from my experience but from many of the folks who have worked on ICONS products and fellow fans of the game as well from whom I have learned much. Thanks for reading!