Generally, well drained soil in full sun, but different varieties have different tolerances and needs, so depends which one you're growing.

Hi, welcome to GoY, there are about 2000 species of Euphorbia's, including annuals, biennials, evergreen, semi evergreen, or herbaceous perennials, deciduous or evergreen subshrubs, shrubs, and trees, and succulents, they range in habitats from temperate, subtropical, and tropical regions, so as Bamboo says, it is near impossible to give an answer, without knowing which species of Euphorbia you have, if you don't have a label on your plant, can you put a photograph of the plant onto your question, and maybe someone will be able to identify it for you, Derek.