YOu can use the following code to design the grid view in order to provide the user with insert facility and then you can use the gridview events to perform the required insert delete update operations:
<asp:GridView ID="GridView1" runat="server" AutoGenerateEditButton ="true" AutoGenerateDeleteButton="true"
AutoGenerateColumns ="false" onrowcommand="GridView1_RowCommand"
onrowdeleted="GridView1_RowDeleted" onrowdeleting="GridView1_RowDeleting"
onrowediting="GridView1_RowEditing" onrowupdated="GridView1_RowUpdated"
onrowupdating="GridView1_RowUpdating" ShowFooter ="true" >
<Columns>
<asp:CommandField ButtonType ="Link" InsertText ="Insert" ShowInsertButton ="true" />
<asp:TemplateField HeaderText ="CustomerID">
<ItemTemplate>
<asp:Label ID="lblcustomerid" runat="server" Text="Label"></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="txtcustomerid" runat="server"></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="ftcustomerid" runat="server"></asp:TextBox>
</FooterTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText ="CustomerName">
<ItemTemplate>
<asp:Label ID="lblcustomername" runat="server" Text="Label"></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="txtcustomername" runat="server"></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="ftcustomername" runat="server"></asp:TextBox>
</FooterTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText ="Phoneno">
<ItemTemplate>
<asp:Label ID="lblphoneno" runat="server" Text="Label"></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="txtphoneno" runat="server"></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="ftphoneno" runat="server"></asp:TextBox>
</FooterTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText ="Address">
<ItemTemplate>
<asp:Label ID="lblAddress" runat="server" Text="Label"></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="txtAddress" runat="server"></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="ftAddress" runat="server"></asp:TextBox>
</FooterTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
YOu can refer the following link to perform insert,delte,update in gridview
Insert, Update, Delete with Gridview....simple way