What is the meaning of 江山入画
入 means to enter, 江山入画 literally means 'the country enters the painting'.
The title 江山入画 (The country in paintings) is very straight forward. you can also interpret 江山 literally  as 'rivers and mountains', and 江山入画 can describe 'rivers and mountains in paintings'  if 山水畫 (landscape painting) is what the main character does
There is an idiom '江山如画',  it means the country is as beautiful as a painting (so beautiful it seems unreal)