First Pen

Guys i just bought a pen and it delivered the next day. I need needles for it i am not realising. I live in the Netherlands and need to get them from a pharmacy apparently.

My question is, i have no idea how to function this pen. Like where do i press on it? I know i should start with .5 ml but here i am looking at this pen, i dont think ill get that tube full with the stuff i see on here. Do i have to have some other substance to mix with.

I am so clueless someone guide me I beg.