If your after bezier curve movement you could check out my “Space Shooter Template” that i have for sale on our site: http://www.tandgapps.co.uk/downloads/space-shooter-template/
If you literaly only want to create a circular path for an enemy to follow you could use a simple function like below to make a set of waypoints that could be used for movement.
The function basically returns an array of x, y points which you can loop through to move an object, which is shown with the enterFrame gameloop function.
--Localise the maths vars.
local mPi = math.pi
local mS = math.sin
local mC = math.cos
local function makeCircle( startPointXY, endPointXY, degreesStart, degreesEnd, yScale, xScale, value)
local xy = {} --Holds the points we make.
local distance = endPointXY[1] - startPointXY[1] --The radius
--Sets the scales if needed.
if yScale == nil then yScale = 1 end
if xScale == nil then xScale = 1 end
if value == nil then value = 2 end
--Changes the direction of the path if needed.
if degreesEnd \< degreesStart then
value = -value
end
--Now create the circlular path!
local i
for i=degreesStart, degreesEnd, value do
local radians = i\*(mPi/180)
local x = (endPointXY[1] + ( distance \* mS( radians ) )\*xScale)
local y = (endPointXY[2] + ( distance \* mC( radians ) )\*yScale)
xy[#xy+1] = {x, y}
--Display a circle to show you the path your making.
local circle = display.newCircle(0,0,1)
circle.x = x; circle.y = y; circle:setFillColor(255,60,60)
end
--Return the array.
return xy
end
--Plug in the needed variables.
--You could also do the yScale, xScale and value but that doesnt need to be put in.
local waypoints = makeCircle( {20,400}, {320,400}, 0, 360)
--Now we are going to move a circle around that path.....
--FIrst create the circle
local circle = display.newCircle(0,0,5)
--Then create the gameLoop function which will run every frame.
local int = 1
local function gameLoop()
if int \<= #waypoints then
circle.x = waypoints[int][1]
circle.y = waypoints[int][2]
int = int + 1
else
int = 1
end
end
Runtime:addEventListener("enterFrame", gameLoop)
Copy and paste that into a blank main.lua file and you can see what it does. Its plug and play!
I’ve done something horribly wrong in there with the y values… Buuuuut it isn’t too bad for 10 minutes work 
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