This code should log you in, provided you enter the correct values for these two lines:
username.Value = "Test"
password.Value = "Test"
Open the VB Editor by pressing Alt+F11 and insert a new standard code module. Paste in the following code:
Option Explicit
Private Sub LoginToEpay()
    Dim IE As Object
    Dim username As Object
    Dim password As Object
    Dim objCollection As Object
    Dim i As Integer
    Set IE = CreateObject("InternetExplorer.Application")
    IE.Visible = True
    'Navigate to the website
    IE.navigate URL:="https://www.epay.com/epayweb/user/login"
    'Wait for page to load
    Do While IE.Busy Or IE.readyState <> READYSTATE_COMPLETE
        Application.Wait DateAdd("s", 1, Now)
    Loop
    'Username and password elements have IDs
    Set username = IE.document.getElementById("username")
    Set password = IE.document.getElementById("password")
    'Login button doesn't have an ID so we must use name
    'This returns an array of items that have the name
    'login
    Set loginBtn = IE.document.getElementsByName("login")
    username.Value = "Test"
    password.Value = "Test"
    While i < objCollection.Length
        If objCollection(i).Type = "submit" Then objCollection(i).Click
        i = i + 1
    Wend
End Sub