Cut a section of gutter liner material to the desired length (cut it long enough to fill the entire run, if possible). For narrow gutters, you'll need to trim the liner to the proper width as well. Slip the liner below the hangers, forming a continuous trough.

Attach downspout adapters and end caps or corner pieces, following the manufacturer's instructions. Connections are usually made with a special adhesive/caulk that the manufacturer provides with the liner.

Repairing Leaky Downspout Joints
A typical place for leaks to occur in the gutter system is at the downspout joints. Over time, gravity can work on downspouts to open joints up, or they occasionally get jostled from below and come loose. A few simple repairs will keep downspout joints tight and reliably leak-free for many years...

Repairing Leaky Metal Gutters
An easy, inexpensive way to repair a piece of metal gutter that has rusted through is to patch it. You can make small repairs using only plastic roofing cement. To repair larger holes, cut a patch from a piece of galvanized metal flashing...