Documents are usually posted to Blackboard courses in a format which you should be able to open and view or, at least, download.

If you cannot open a document directly, or print from within your browser, try downloading the document to your local computer and opening it in the appropriate application, e.g Word, Powerpoint, Excel. To do this, right mouse-click on the link to the document, and select "Save Target As / Save Link As (Wording will differ depending on your browser), save the file to your machine.

For some documents you may need to download a 'plugin' to read them, e.g. Adobe PDF files can be read using the free Adobe Reader plugin.
If the file is in a format that that you cannot open please consult with the lecturing staff who have uploaded the document to Blackboard.