I had help with this task. Adjusting any bearings on a bicycle can be fiddly, but with patience you will always get there in the end!
Here is my Instructable on the first step of rebuilding my bike.
Fitting the forks and headset!
Forks: the bit of a bike that holds your front wheel, and steers!
Headset: the parts of the bike that attach your forks to your frame, and allow them to spin freely.
Step 1: Bare frames, back from the painter's workshop.
Step 2: Prepare your headset components for rebuilding.
Cut the cabletie, and lie the headset parts on your worktop in the right order, the right way up!
Clean each component to remove old grease and dirt, any solvent will do.
Whilst cleaning, check any part for signs of damage or wear.
A nice trick is to run a ballpoint pen along the surfaces that the bearings touch, if you can feel roughness through the pen, that part probably needs replacing.
We recommend buying new bearings rather than reusing your old ones.
Step 3: Fit headtube races.
We were lucky enough to have a proper headset press tool which makes installing the races a doddle.
If you haven't got access to the proper tool you could press them in with a large vise, being careful not to damage the races.
You can also knock them in with a mallet, but put a woodblock on top of the race so you don't damage them!
When properly installed, both the races should fit snug in the headtube and be in line with each other.