You can toast pecans in a preheated 350 degree oven, or in a pan on the stovetop.
To toast them in the oven, place the nuts on a parchment-lined baking sheet in the preheated oven and bake for about 5 minutes. They will develop a nice 'nutty' aroma as they toast. Watch carefully as they burn easily. Remove them from the baking pan as soon as they are out of the oven, as they will continue to cook with the remaining heat from the pan
I prefer to toast nuts on the stovetop so that I can keep a closer eye on them. Put the nuts in a pan or skillet and place on medium-low burner. Stir occasionally until the nuts begin to brown and smell aromatic. Remove from the heat.