Typing this from memory, so please forgive typos:

SELECT p.FirstName, p.LastName, p.LoginName, a.EnterpriseName, a.PeripheralNumber, sg.SkillTargetID, sg.EnterpriseName

FROM Agent a

INNER JOIN Person p ON a.PersonID = p.PersonID

INNER JOIN Skill_Group_Member sgm ON a.SkillTargetID = sgm.AgentSkillTargetID

INNER JOIN Skill_Group sg ON sgm.SkillGroupSkillTargetID = sg.SkillTargetID

Let me know if this does not work for you

Sam