Fixing a chainsaw will depend on the specific problem you're experiencing. However, here are some general steps you can follow:

1. Check the fuel: Make sure there is fuel in the chainsaw and that it's fresh. Old or contaminated fuel can cause starting problems or make the chainsaw run poorly.

2. Check the spark plug: Remove the spark plug and inspect it for damage or fouling. Replace the spark plug if it's damaged or dirty.

3. Check the air filter: A dirty air filter can cause the chainsaw to run poorly or not start at all. Remove the air filter and clean or replace it as necessary.

4. Check the chain: A loose or dull chain can cause the chainsaw to perform poorly. Make sure the chain is tight and sharpen it if necessary.

5. Check the carburetor: The carburetor can become clogged with dirt or debris, causing the chainsaw to run poorly. Clean the carburetor or have it professionally serviced.

6. Check the fuel lines: Cracked or damaged fuel lines can cause the chainsaw to leak fuel or not run at all. Replace any damaged fuel lines.

7. Check the starter rope: If the starter rope is frayed or damaged, it may not pull smoothly and can prevent the chainsaw from starting. Replace the starter rope if necessary.

8. Check the ignition system: Faulty ignition components can cause the chainsaw to run poorly or not start at all. Have the ignition system tested and repaired if necessary.

If you're unsure about any of these steps or are experiencing a problem that you can't diagnose or fix yourself, it's best to take the chainsaw to a professional for repair.