Somewhere in here is a post with instructions from JamesP. I will find it, but for now, here is an overview:
1. Select whether you want Metric, US, or Imperial.
2. Select Check box for additional sugars, select the type of sugar and the amount.
3. Select Check Box for Target Volume and enter the batch size.
4. Hit the Calculate button.
This will give you the SG and potential ABV for the mead. If you want to change the sugars, or add ingredients, go ahead and then just click calculate to get the result.
If you want to know how much honey to add to get a specific SG:
1. Do not check any of the Additional Sugars boxes.
2. Check the Target Volume and enter the batch size.
3. Check the Target Gravity box, enter your target SG, and hit calculate. The Additional Sugars #1 will change to show you how much honey is needed.
Hope this helps for now.
Angus