Using a skill injector will add unallocated skill points to a character. If any unallocated skill points are available, their amount will listed at the bottom of the “Skills” section on the character sheet.
The “Apply Skill Points” button will apply all available unallocated skill points to the current training queue.
Unallocated skill points can also be put towards an individual, trainable skill that is not currently being trained by the character. This can be done by finding the respective skill within the character sheet and selecting "Apply Skill Points" from the context menu that pops up with a right click on the skill.
This will open the "Apply Skill Points" dialogue, where the amount of skill points to be placed into the selected skill can be specified.