Event: Time eplapsed 5 seconds (dialogs do not show up on map init)
action: dialog - clear mydialog (make mydialog variable as new dialog in variable windows ctrl b in trigger editor you dont have to call it mydialog i did just for wrtiing purposes)
dialog - change title of dialog to 'the dialog'
dialog - create button for mydialog name 'button'
setvariable - set button = last created dialog button (I almost forgot.. you need to make a variable as a dialog button same as first step but as a dialog button not new dialog)
dialog - show dialog to 'whatever player'
for more buttons just repeat the last 2 steps.
Then to work it
Event - dialog button click
condition - dialog button cliked = button
action - what ever you want the button to do.
hopefully that should be failry clear pm me if you still dont get it