For SilicaCAD 2017 or older versions. 
Save the last rendered image: 
From the menu View select Render > Preferences 
— Under the tab General press the button “Save Last Render to File” (or “Redisplay Last Rendered Image” to see the created render on the screen) 
— Specify the path and the name with extension for your output file and confirm. 
Save the render directly to file: 
From the menu View select Render > Preferences 
— Under the tab General  “Render to file” define the desired size and press the button “Render” ( the button on the right of the “File” field ) 
— Specify the path and the name with extension for your output file and confirm. 

Starting from SilicaCAD 2018:  
— From the View menu choose “Render > Open render”  
— Perform all render configurations you need  
— Run render operation by using the “Full render” button  
— Use the “Save the last render on file…” button   
For advanced settings please refer to the integrated render guide