The verses of "Weyitten Lekha" should be said on Mosei Shabbath. Rabbenu the Ari, z"l, used to say them at the time that he recited Habdalah, with a cup of wine, in his home. However, the prevalent custom is to recite them after Habdalah.
Those who recite Habdalah in Synagogue, say the verses as soon as they return home. Some Ashkenazim have the custom of reciting them in the Synagogue.
When Mosei Shabbath falls out on Yom Tob, the verses are not recited. The reason is that the essential point of the blessing is for success in one's livelihood and no business is transacted on Yom Tob. Nevertheless, when Mosei Shabbath falls on Hol HaMo'ed (the intermediate days of a Festival), Weyitten Lekha is recited.
(See Meqabsiel, 2nd year, Wayyesei, Oth 62)
Veyiten Lecha, weyitten Lekha, Moztzei Shabbat, Motzoei Shabbos, Mosi Shabbath