Applying epsolm salts?

Do I just mix the epsolm salts in my water or should I pour it on top of the soil? Your help is very much apreciated. Thankyou in advance.

1 teaspoon per gallon of water

what exactly does that do i thought epsom salt was used for treating poisen ivy and ect.

its cheap and has some nutes that the plant can use. and it ajusts ph i think.
oh and its a US gallon not a UK gallon.

no, it has no nutes, it doesn't adjust the pH. It provides the plant with magnesium and sulphur, but people use it to treat mainly mag deficiencies.

dont just add it to the water, it is best to crush it first then dissolve it in water.

Dosage varies. I've seen mostly 1TBS per gallon on RUI? Personally, I add 1/4 tsp per to almost all my waterings. NEVER have yellowing issues.