How to place cells if you have 500 points?
Can only figure out to put one at a time
Which software, and which version of the software are you using?
Do you have a list of point coordinates where these cells need to go? If you do, there are options. If you are using CONNECT, you can use the Import Coordinates tool (https://docs.bentley.com/LiveContent/web/MicroStation%20Help-v18/en/ImportCoordinates.html) to import your point coordinates as cells. The corresponding tool for V8i is also called "Import Coordinates, and is found on the XYZ Text toolbar.
Microstation 08.11.09.919Power GeoPak 08.11.09.918Power InRoads 08.11.09.918
without knowing more details, it's complicated to provide any advice (please see the best practices what information should be shared and how).
When you have 500 points in a format of text file, Import coordinates tool, mentioned by Mary, is the place where you should start. When more complex workflow is required e.g. to fulfill specific requirements, often a help of VBA macro is necessary.
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As MaryB and Jan have suggested you need to provide more details. If your text file contains the cell name and its coordinates you could follow the instructions in this wiki