Perennials come back year after year if left undisturbed. Most do not bloom the first year but develop roots and foliage to support flowers the next year and after.
Set irises and yuccas with roots barely covered with soil. Plant peonies, lilies of the valley and hostas with buds 1-2 inches below the surface of the soil. Set plants with a distinct crown with the crown even with the soil surface. Plant those without a distinct crown, that look like a chunk of root, 1 inch deep. If you can't tell which end is up, lay the root on its side. Some plants with distinct crowns should be planted with the crown 1 inch below the soil.