Professional dry cleaning or laundering is always the safest method of cleaning slipcovers.
If the fabric was produced for slipcover use, it has been pre-washed to prevent shrinking, and may be machine washed at home in cold water using the gentle cycle. Non-detergent soaps i.e., Ivory, Dreft, etc. is best.
Use the air dry setting, low temperature only, when using the dryer. Remove the slipcover from the dryer while it is slightly damp. Put the slipcover on the sofa body and cushions immediately to maintain shape of the cover.
Tuck slipcover into corners of sofa base for best fit.