Hey there! So first you need to know the molecular formula for Barium Chloride which is BaCl2. This will show what cation Barium will form which is Ba2+. This information is important to know how many electrons you need for it to be reduced. Now you just need to do a little dimension analysis. The units of the final answer that you aim for is in Ampere or coloumb/second. I've posted the solution below. This is just basically the mass you want to have converted to grams, multiplied by molar mass, number of e- per mole you need to reduce and faraday's constant divided by the time exposed, converted to seconds. I hope this makes sense.