Crank sliding horizontally through the bottom bracket Was out biking today when I noticed the pedals were moving side to side, with the pedal arm almost coming off the left side. As I was investigating the washer with "LH fsa AL" actually came off in my hand. I re-installed it and tightened it up by hand, but obviously its tight with a big gap between the pedal arm and the bottom bracket now as below.

Is it simply a matter of removing this washer, pushing the arm back towards the bottom bracket and tightening it? And if so what tools do I need? I've got allen keys, screwdrivers and various other general tools, but I haven't got anything with 6 holes like it looks like id need to remove it.
Thanks
You need a large allen key, often an 8mm to tighten that centre bolt right down.

It'll pull the crank arm onto the spindle and secure it.

The LH-FSA-AL ring is the self extracting bolt, the internal hex bolt pushes on the back of it to pull the crank off without extra tools. That has a left hand thread so that it doesn't unscrew as the internal bolt unscrews. It only really needs to be tight enough to stop it from coming out, finger tight probably isn't enough though.

You need a pin spanner for this which is a pretty specialised tool, I've certainly never had need to buy one, so you might want to pop down your LBS and ask them to tighten it up.