If the holes are not completely lining up or you want a more secure install use wall anchors to attach the vanity to the wall.
How to install a new bathroom windows on existing wall.
Then examine your studs.
In this arrangement an existing wall stud is used as a king stud on one side and a 2x2 or 2x4 cleat is attached to the stud on the other side to provide a nailing surface for patching the drywall after the window is installed.
Making a small 6 x 8 ft bathroom feel larger.
Shims are used the level the window.
Old wooden windows have stops holding the sashes in place.
Interior stops parting stops between the two sashes and exterior stops.
Installing a state of the art residential wall hung toilet and sink.
Identify any stops on the existing window.
Place the window into the frame.
Although this new bathroom is a bit smaller because of additional plumbing walls it appears larger.
If you re installing from the inside remove the interior stops and leave the exterior stops in place.
Flashing band should then be installed around the window on the outside.
Add screws at the bottom to stabilize it.
Check the level again before trimming the shims with a utility knife.
The person inside should then shim between the window and the framing to keep the window in place image 1 image 2.
Having fewer dirt catching corners and edges simplifies floor cleaning.
Use a level to make sure the window is straight.
The flashing should be nailed into place.
If there are large gaps at the wall or floor attach quarter round moulding along the wall or floor edge with finishing nails.
Shims can be glued into place or tacked with a trim nail.
Add two screws one in each corner to hold it in place.