It will be awesome for you to go on a directional now, before you get the "bad" TT habits, that only makes the transition worse
The sooner the better, and I know you'll enjoy the feel because of being a windsurfer and loving the "drive" a directional has
And as an ex windsurfer you should be able to go both ways really good, and not have a really weak side (you will love this when riding waves later)
Above posters advices are good.
Just - please DO change stance really often (switch feet / jibe), as you are used to jibing, and this is a must in waves and will give you endless options - besides being awesome to learn and do
Dont go into the classic mistake - riding mostly on the preferred stance (meaning toeside most of the time)
But no need to tell you, if you were an okay windsurfer.
Forward strap positions are the best, for starters.
Later, you will most likely move the rear strap aft, and only use it when riding steep waves or jumping - otherwise, going upwind or in light wind, you stand in front of the rear strap.
But to start out, just use a relatively forward rear strap position, as you are quite new - and learn to ride toeside as said - but jibe as often as possible too.