First off, I want to point out that because bishops are lay leaders from various professions, they aren't trained or professionals in these areas. Thankfully, many bishops recognize this and are quick to refer people facing such problems to professional counselors and therapists.
While I can't access it, the first handbook does have a section on handling abuse. There are training videos for bishops on dealing with abuse, but not all bishops have heard about them (which might start changing now) (source).
In 2002 President Hinckley said,
For a long period now we have worked on this problem [abuse]. We have urged bishops, stake presidents, and others to reach out to victims, to comfort them, to strengthen them, to let them know that what happened was wrong, that the experience was not their fault, and that it need never happen again.
We have issued publications, established a telephone line where Church officers may receive counsel in handling cases, and offered professional help through LDS Family Services.
These acts are often criminal in their nature. They are punishable under the law. Professional counselors, including lawyers and social workers, are available on this help line to advise bishops and stake presidents concerning their obligations in these circumstances. Those in other nations should call their respective Area Presidents.
Like with anything, there are limitations. Again, bishops are lay leaders without professional training. Bishops (at least in the past) weren't allowed to counsel members to divorce, which can be a problem in cases of serious abuse. There can be issues as bishops tend to work more closely with the men in their ward, and may be more willing to trust these men's stories and their perceived integrity over their wives' words (which some say happened in the case of Rob Porter).
I just want to say that the tendency to distrust women and their abuse is not limited to any church, but is one that faces society. While it is heartbreaking these women had to go through this abuse, it is a start to opening up a conversation on what we can all do better to end abuse.
-guppy of doom