1 - main character
2 - main character
3 - main character
4 - main character
5 - Forad Darre
6 - hired NPC
7 - hired NPC

You can press the corresponding number to access each party member. I believe that hitting 1-4 just opens your inventory. But hitting 5-7 should bring up a conversation screen for Forad Darre and your hired NPC's. From there you should be able to dismiss them from your group (but you cannot fire Forad Darre, you are stuck with him). If you have hired a gatemaster or someone like that then that should also be one of the conversation options, in other words there should be something in that screen to get them to cast town portal or water walk or healing or whatever. If the skills you are referring to are combat spells or fighting, then those should just be activated by hitting the right mouse buttons or keys during a fight.