These Euphorbias are very popular at the moment.
In the ground or in a pot, the Cowboy provides a great architectural feature with the popular Palm Springs vibe.
They prefer a sunny position in well drained soil or preferably a premium “cacti and succulent ” mix. They can be grown indoors but will need a very well lit spot with good ventilation.
Let them dry out completely before giving them a good water again.
Give the some slow release fertiliser at the start of Spring.