Linux: Macaulay2 (including Schubert2!) is part of the standard distribution, at /usr/bin/M2. This may not always be the latest and greatest version, so if you need that, ask Stein Arild or Jan-Magnus for directions.
Mac or Windows PC: You may also run Macaulay2 on your Mac or Windows PC, follow the instruction on http://www.math.uiuc.edu/Macaulay2.
Tags: Mathematics, Software