Magnesium with food?

Hello, sorry for noob question but I got told other day my plant got a magnesium def or lockout on my plants, so I went and got some but I'm unclear if I put it in with the food as the bottle dosn't say! I feed them 5L each of diluted terra Flores and the bottle of magnesium says x amount per litre. I have looked about but I can't find anything that says.

Could someone help?

I'm also considering getting some molasses and bud booster to feed my plants....would I just mix the nuts, mag, boost and molasses all in the same water? I don't really understand what to do, thanks.