Step1

Start DynamicDesigner 

Click Motion on the pull-down  menu.

Step 2

Add New part

Set automatically add new parts to grounded or moving part.

Click on Yes button.

Step 3

Delete joints

Delete unnecessary joint. Selected joint will be changed into green.

The useless joint must be deleted. 

Step 4

Delete joints

Delete unnecessary joint. Selected joint will be changed into green.

The cylindrical joint must be deleted and substituted with translational joint.

Step 5

Insert Joints

Click on the Insert revolute Joint button.

It is for link4 part.

Step 6

Select Moving Part

Click on link4 part.

Step 7

Select reference part

Click on upper link3 part.

Step 8

Select joint location

Click on the hole of link4 part to locate revolute joint.

Step 9

Select  rotation direction

Click on the hole of link4 and click OK button.