If you have Campden tablets they are a lot easier in terms of measurement for 1 gallon batches. If you buy campden tablets make sure they are Potassium Metabisulfate and not Sodium Metabisulfate. I've never seen the latter but they are said to exist & are NOT the best choice.
1 Campden tablet crushed well and dissolved in an ounce or two ounces of warm water, add to the carboy you are going to rack the wine into and rack into it.
One good thing about Campden tabs is that there is no measuring involved. K-Meta powder for 1 gallon needs to be measured with a digital scale if possible.