You can do it by using Sticky Side Buttons plugin. Follow these steps:
- Install and activate the plugin.
- Head to Sticky Side Buttons menu into your WordPress dashboard.
- Click on Add Button. A box will open up, showing the options for
adding text, icon, link, and color for the button. - Under the General Settings section, you will find options for
Button Positions, Rollover Style and Animations. Choose your desired settings. - Finally click on Save Changes button.