Well now you have a problem somewhat bigger than deciding what product to use to repair the damage - you need to wait for the salt to be flushed away thoroughly before you attempt to re-seed any bald patches. How fast this happens depends on how much salt you applied, whether you applied it more than once, and how much rain you get to flush it away. Without more info about where you are, and the quantities used, its impossible to say when that might be.

Next time you want to get weeds out of your lawn, use a specific lawn weedkiller - Resolva ready mixed Lawn Weedkiller can be used directly on weeds, or you can buy something like Verdone and water the whole lawn with it. Neither of these will kill grass, they only work on broad leaved weeds.

thank you for reply, so after a pretty good soaking shoul i apply a mixture of seed and fertiliser patch repair ?

Don't know - how much salt did you use, how long ago, do you live in a high rainfall area? Have the dead patches of grass expanded at all in the last week or two, are they still expanding? One soaking isn't going to do it I'm afraid, but be easier to say how long if you add the extra info I've asked for. If you don't want to wait, then work a fine tilth on the bare patches and chuck some grass seed down, keep it watered - that's the cheapest option to find out if the soil's still toxic. Patch Magic is very expensive, you wouldn't want to cough up for that only to have it all not grow or die because of salt toxicity.

I don't think a lot of people who aren't proper gardeners understand why their location/environment is important, Snoop, when they ask their questions.