Upload, Import one single value to amibroker?

I have calculated Implied volatility of an instrument. Now I want it to upload it on amibroker so that I can get a line chart of it. I only have the closing price of it. Please tell me how can I do it ?

If I understand correctly, you can use the method described here in detail.

You can store the computed data to AUX1/AUX2 field without the need of altering any existing data.

Thanks for the link. I think the link is for combining additional data with already existing data.
But here I want to create a new symbol named "abc" and then only plot closing price.

You have not mentioned anything like abc in your first post or new symbol.
If you don't want to combine additional data, then just use ASCII importer and add a new symbol.