Securities & Shares received as gift should it be shown in ITR, if yes how & where?

Yes,you need to show this in your ITR. Since you have received it from your grandfather (a lineal ascendant), it is not taxable and thereby exempt in the hands of recipient (i.e.. you) u/s 56(2)(x). So you can show such gift under the schedule of EXEMPT INCOME and show the total actual cost of acquisition incurred by your grandfather or the F.M.V of the shares received as on 31/01/2018 whichever is higher (because now LTCG tax applicable on sale of shares as and when sold by you)