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The article gives the margin of error for a $95\%$confidence level as $3$percentage points.

The margin of error is the amount of error that is made, on average, in estimating the population proportion $p$by the sample proportion $\hat{p}$.

Thus on average the sample proportion will be within $3\%$of the true proportion in $95\%$of all samples.

The article gives the margin of error for a $95\%$.

$\hat{p}=66\%=0.66$

$E=3\%=0.03$

The boundaries of the confidence interval is the sample proportion increased/decreased by the margin of error:

$0.63=0.66-0.03=\hat{p}-E<p<\hat{p}+E=0.66+0.03=0.69$

We are $95\%$confident that the true population proportion is between $0.63$and$0.69$.

The article gives the margin of error for a $95\%$confidence level.

The confidence level is $95\%$.

This means: On average, in $95\%$of all samples the corresponding confidence interval will contain the true population proportion $p$.