To plot a position using Lat / Lon scales...
(1) Double check the Lat value from original source.
(2) Identify this Lat on the Lat scale on the side of the chart, double checking the tick mark spacing before hand.
(3) Use plotter or dividers to transfer this latitude to chart and draw a short line in your approximate position.
(4) Repeat the process using the Lon scale at the top or bottom of the chart. Draw another short line to intersect the Lat line, and the intersection is your position.
(5) If this is a position fix, draw a small circle around the intersection and label this position with the time.

General Notes
There are numerous ways to carefully plot a Lat / Lon position. The key issue is doing it precisely. In these days of GPS, much of our position navigation has been reduced to simply plotting a position on the chart. Needless to say, we don't want to do a bad job of all we have left!

But, jokes aside, this is a crucial part of navigation regardless of how we got the info in the first place. And it is one of those things that seems so easy, we might not treat it seriously enough. Which is a mistake. It cannot be done too carefully in most cases.

If the plotter won't reach the region of your position as shown in the video — which it certainly won't in many cases — then we have a bit more work to do. First, on the latitude scale itself, set the dividers to the distance from the given latitude to the nearest parallel shown on the chart, and then mark that distance on the chart near the approximate longitude. Then use plotter to draw the short Lat line at that position, rolling the plotter down from that nearest parallel. Then do the same for the longitude.

Video Notes
In this example, the first step shown is the doublechecking of the latitude tick mark spacing, by counting off the steps between the two labeled latitudes. Here the bold bands mark off 1' intervals from 36° 50' on up. One divider tip is then placed at the 52.7' mark and the plotter is rotated till it is parallel to a latitude line. In this case, this was performed by aligning the vertical line in the center of the plotter with a meridian on the chart.

Once the plotter is parallel, it is slid up to the divider tip to mark the proper latitude, and a short line drawn in the region of the position. We know where this should be from looking at the longitude scale and the longitude we must plot.

Then the process is repeated for the longitude.

The conventional plotting symbol for a position fix is a full circle about the intersection. Other positions on a chart are marked with other symbols, such as a half circle for Dead Reckoning positions, and a square or triangle for estimated or projected positions.