To infuse a sphere scroll with materia, select infuse from its subcommands. Each sphere scroll can be infused with up to 7 types of materia, granting a bonus to the corresponding attribute. The materia is consumed upon use. While grade I materia satisfies initial infusions, progressively higher grades of materia is needed to enhance an attribute past certain points. There are limits as how many times an attribute can be enhanced. Each infusion requires the use of Alexandrite. A maximum of 11 materia per type and grade applies. For example you might use 11 Savage Might Materia I and 1 Savage Might Materia II, but not 12 grade I materia of the same type. The first 6 of a type and grade automatically succeed. After that the chance reduces to 96%, 90%, 82%, 72% and finally 60%.
Once you have infused a sphere scroll with 75 materias (for Paladins the amount of materia is split into 53 for Curtana Novus and 22 for Holy Shield Novus), Jalzahn can use it to enhance corresponding animus weapon. Once completed; it is possible to change the stats by obtaining a new Sphere Scroll and transferring your weapon stats across: see here.