Few TVs have a horizontal linearity control,
so don't be disappointed if there isn't one on your unit.
The most likely reason for the problem is aging capacitors.
Carbon resistors change value as they age, so they can be troublesome, too.
Another possibility is that the deflection yoke has shifted position.
In a B&W set, that isn't a big problem to correct,
but in a colour TV it is best left to an experienced professional.
Get a Sams Photofact that covers your model and see what parts look likely to be bad.
Whatever else you do, DON'T ADJUST THE SLUGS IN THOSE CANS!
More radios and TVs have been f**ked up by people messing about with IF transformers
than by any other common means.
If they Do need adjustment, pass the job to someone who knows how.
ONLY plastic and fiberglass tuning tools should be used.
Metal tools will seriously interfere with the function of the transformers.