This depends on what type of surgery you have had. In general, if you have had a repair (e.g. rotator cuff repair, labral repair, instability repair) then the sling is worn all the time for 3 weeks, (including sleeping) unless you are doing your exercises, taking a shower, or sitting comfortably.
For example if you are watching television you may take your sling off and rest your arm in a comfortable position or if your wish to type on a computer or write you may sit at a desk, take your sling off, rest your arm on the desk and type or write. However, when you are up and walking even if in the house, it is safest to use your sling to avoid any inadvertent injury (i.e. fall, sudden motions)
If you have had only a decompression type procedure (e.g. subacromial decompression, acromioplasty, distal clavicle excision) or a procedure to gain motion (e.g. capsular release for frozen shoulder) then your sling is for comfort only. You may take your sling off as soon as possible and begin moving your shoulder.
If you are having trouble wearing your sling please contact COG.