I edited my question because I had asked the wrong question. I know how to take up the slackness of belt by rotating the engine by hand and adjusting the belt tensioner bolt. This is not what I want to know here. I have learnt them in my previous question thanks to my friend HandyHowie.
What I need to know here is the very stage of just putting the belt on the pulleys and sprockets correctly. Do you pull the belt a little bit by hand to install it straight and level between the pulleys and prevent to shape it like a curved line?
This is what I need to know:
**When sliding on the new belt, keep the slack near the tension pulley — all other belt running should be tight. This will help keep proper alignment as the tensioner pulley is tightened. **