If you really want to use an old seed from the light wallet, (you’ve probably copied and pasted this seed many times before) - it is possible import it into Trinity without typing the 81 character seed.
Ridiculous. Most users without clipboard protection wouldn’t have key logging protection or use a virtual keyboard to type out the seed.
NOT RECOMMENDED procedure;
-Download, verify & install Trinity.
-Generate new seed, export it using “export SeedVault” (this produces a kdbx file)
-Close Trinity
-Edit the kdbx file with KeePass to replace the new seed with your old seed. (Paste your old seed into the password sections)
-Save it with a different name, e.g. OLD SEED
-Delete entire contents of AppData\Roaming\Trinity
-Open Trinity
-At the seed generation step, select "no, I have one already" then drag the OLD SEED seedvault kdbx file into Trinity.
Proceed through until the program is up and running. It should display the correct balance relating to the old seed. There are 2 tools available to refresh things if it’s not displayed.
It is less secure to keep funds on an old seed from the light wallet. Don’t follow the instructions above.
To secure your IOTA funds effectively;
-Create a new seed in Trinity & use the SeedVault feature to export a secure backup of the seed.
-Transfer funds from the lightwallet (your old seed) to your new account in Trinity.
-Keep several backups of the SeedVault kdbx file, and keep your password secure.