documentclass[a4paper, 12pt]{article}

usepackage[acronym]{glossaries}

setglossarystyle{alttree}

makeglossaries
newacronym{frc}{FRC}{First Robotics Competition}
newacronym{ftc}{FTC}{First Technical Challenge}
newacronym{fll}{FLL}{First Lego League}
glsaddall
glsfindwidesttoplevelname

begin{document}
  section{Sample Text}
  gls{frc}, gls{ftc}, gls{fll}

  printglossary[type=acronymtype]
end{document}