Permission Issue in SharePoint O365 - sharepoint

Question

I created a trial office 365 sharepoint account for learning. While creating my first Insert operation I got an exception as
Access denied. You do not have permission to perform this action or access this resource.
My code is
In Load event
protected void Page_Load(object sender, EventArgs e)
{
var spContext = SharePointContextProvider.Current.GetSharePointContext(Context);
using (var clientContext = spContext.CreateUserClientContextForSPHost())
{
if (clientContext == null) return;
Session["clientContext"] = clientContext;
Microsoft.SharePoint.Client.User spUser = clientContext.Web.CurrentUser;
clientContext.Load(spUser, user => user.Title);
clientContext.Load(spUser, user => user.Email);
clientContext.ExecuteQuery();
}
}
On button click save event(Name and EmailId)
protected void Button1_Click(object sender, EventArgs e)
{
try
{
using (var clientContext = Session["clientContext"] as ClientContext)
{
if (clientContext == null) return;
var oList = clientContext.Web.Lists.GetByTitle("SharePointTestList");
var listCreationInformation = new ListItemCreationInformation();
var itemToAdd = oList.AddItem(listCreationInformation);
itemToAdd["EmailId"] = TextBox2.Text; //My List
itemToAdd["Name"] = TextBox1.Text; //My List
itemToAdd.Update();
clientContext.Load(itemToAdd);
clientContext.ExecuteQuery();
}
}
catch (Exception ex)
{
Response.Write("Error Occured"+ex.Message);
}
}
It seems some permission issue. But I am not able to figure it out.

Answer 1

I have already faced the same problem while creating 1st time.I solved it by doing like this
Go to AppManifest.xml in your SharePointApp
Click Permissions Tab
Give FullControl Permissions to Scope Web and List

Answer 2

As already discussed in the comments I have a strong suspicion, that you are lacking the proper permissions to write to your target list.
As you've said you have "limited access". This means:
Can view specific lists, document libraries, list items, folders, or
documents when given permissions.
In order to write to a list, you need to grant the user at least "Contribute" permissions.
So this is not a programming related issue. Read up on the basic permission levels within SharePoint here.