Poe2 spear stab

Help I was just wondering how you put more support slots in the spear stab skill when it’s got a grey circle on the skill bar. Can use skill but can’t upgrade it or put more support gems slots in. Only have the 2 default slots. I’ve seen some build guides that have 5 gem slots in spear stab. Couldn’t find a separate spear stab gem. Only the one inherent to the spear. Thanks.