Before mounting covers into any sort of album, one should store them in either glassine envelopes or in special plastic holders (slightly larger than the covers and with an opening on one end). Many kinds of cover albums are available most of them with plastic pages with compartments for each cover and similar in many ways to a stockbook. Like a stockbook, these cover albums allow one to arrange and rearrange one's covers at will.
When it comes time to mount covers onto album pages (similar to the album pages described above for stamps) one simply uses gummed or pressure-sensitive mounting corners for placement into the album. NEVER use hinges to mount covers. No cover should ever be allowed to end up having the kind of residue on the back that a hinge will leave. If you have any questions about storing and/or mounting your stamps and covers, just consult a professional stamp dealer or experienced collector.