1. First download the activiti-designer-5.18.0.zip file from http://activiti.org/download.html.
2. Unzip activiti-designer-5.18.0.zip and delete artifacts.jar and content.jar. 
3. Create the eclipse folder in activiti-designer-5.18.0.zip. 
4. Move the features and plugins folders into the eclipse folder. 
5. Move the activiti-designer-5.18.0 file to the root directory of the F drive.
6. Then switch to your eclipse installation directory, enter the dropins folder, create a new activiti.link file, and write the file content path=D:/activiti-designer-5.18.0. As shown in the figure below: 
7. Restart eclipse, clean the eclipse cache before restarting, click eclipse, select properties, and the eclipse properties box will pop up, as shown below:
(Add -clean to the target box) 
8. After setting, open your Eclipse, check whether the installation is successful, create a new one in the blank of Project Explorer, select other. After the pop-up box, search for activiti to exist, if so, the installation is successful . As shown below: