How can a cell be placed in a *.dgn file with Microstation?
You need to click on cell icon: Place Active Cell
V8i:
Connect Edition
Then in the Place Active Cell window click on the dots:
the Cell Library windows open. From here you are able to choose your libraries:
File>Attach file or File>Attach folder
It is also possible from here to create a new cell. Please have a look at this second wiki article: https://communities.bentley.com/products/microstation/w/microstation__wiki/32001/how-to-create-cells-in-microstation-v8i-and-connect-edition
https://communities.bentley.com/products/microstation/w/microstation__wiki/32001/how-to-create-cells-in-microstation-v8i-and-connect-edition