Ectomorphs will have a hard time gaining weight and muscle mass; training should be focused on compound: multi joint, weight bearing exercises.
Ectomorphs will generally have a fast metabolism and burn calories rapidly.
Mesomorphs can develop and build muscle mass without much difficulty, and can usually eat without fear of gaining fat.
Mesomorphs are athletic by nature, so training can consists of any individual preference.
However, one aspect to keep in mind when you start training is body type- also know as somatotypes, created by William Sheldon (1899-1977).
Each human being is genetically unique: no two humans are the same.
In case you have age spots you will appreciate that there is a recipe in the program which can help with that also.