The timekeeping is adjusted with the rating nut at the bottom of the pendulum.The rating nut keeps the bob (typically a brass disk)  at the correct position as you  adjust the length of the pendulum for accurate timekeeping.

To make the clock run slower: Turn the rating nut to the left or lower.

To make the clock run faster: Turn the rating nut to the right or up.

It may be helpful to keep a log of the adjustments made and error found each day as you regulate. This will be  trial and error, and can take a week or two of daily adjustments, until you get the clock keeping time. The amount of adjustment will vary depending on the amount of error, and the length of the pendulum.

A grandfather clock with a long pendulum may only vary 30 seconds in 24 hours with one complete turn of the rating nut. It could change a mantel clock with a very short pendulum approximately 2-5 minutes, with the same  amount of adjustment.

Be sure to use an accurate clock to check the clock you are regulating. A quartz or electric clocks is probably best, rather than a mechanical clock. There are other factors to consider when adjusting timekeeping:

A worn or dirty mechanism can be irratic in timekeeping. In other words, it may gain time one day , and without adjustment, lose time the next. If you experience this, the clock will need repairs to overcome this. A spring driven clock would be considered good if it is within a minute a week, where a weight driven clock can be adjusted to within a few seconds a week. Keep in mind the condition of the movement, how stable it is sitting or hanging, and how even the tick (in-beat), can all be factors in timekeeping. The change of temperature, barometric pressure, and altitude are also factors. This is why a clock will normally need adjusting in timkeeping when it is relocated.