Could do it in a few ways but the easiest way would probably be a generic for loop that repeatedly changes the number of periods until the game has loaded or whatever your condition is.
while not hasLoaded do
for i = 1, 3 do -- you could change it to be any number but 3 is probably the best
label.Text = 'Loading' .. string.rep('.', i)
task.wait(0.5)
end
end