New bike size concern

cooldad

Scale on bars just shows the angle it's at so you can take it apart and put it back in the same place.

Black thing is just to stop the fork legs getting squeezed together and damaged in transit (and handy to stop the ends getting scratched) - just pull it out. Useful to keep in case you need it again.

cooldad

The marks on the bars also help you centre them - yours are a bit to one side.

manhattan24

Great. Have now put on the front wheel and sorted the handlebars.

I noticed that on the top of the handlebar stem there seems to be a largish allen key adjustment with a disc that seems a bit loose, does that need to be tightened too?

Thanks

cooldad

Read Parktools.
Specifically Threadless headset service. The round jobby is the top cap used to pretension the bearings. The stem bolts the hold everything in place. Once they are tight the top cap and allen bolt don't do anything.
Providing they were adjusted correctly in the first place.