Wizardstep should go by order

<style>.sidebar
{
    display:none;
}
</style>
// add style to NavigationButtonStyle and SideBarButtonStyle it will hide those side bar
<asp:wizard id="Wizard1" runat="server" navigationbuttonstyle-cssclass="sidebar"
        SideBarButtonStyle-CssClass="sidebar" ActiveStepIndex="0">
    <WizardSteps>
        <asp:WizardStep ID="WizardStep1" runat="server" Title="Step 1">
            //all your design after then one button
            <asp:Button ID="btnNext" Text="NextStep" OnClick="btnNext_Click" runat="server" />
        </asp:WizardStep>
        <asp:WizardStep ID="WizardStep2" runat="server" Title="Step 2">
            //all your design after then one button
            <asp:Button ID="btnNext1" Text="NextStep" OnClick="btnNext1_Click" runat="server" />
        </asp:WizardStep>
    </WizardSteps>
</asp:wizard>

protected void btnNext_Click(object sender, EventArgs e)
{
    // all your desired code for example save your first step data
    Wizard1.ActiveStepIndex++; // go to 2nd step
}
protected void btnNext1_Click(object sender, EventArgs e)
{
    // all your desired code for example save your first step data
    Wizard1.ActiveStepIndex++; // go to 3rd step
}