If I understand you correctly, you have the 12 words that were randomly generated by electrum + 1 extra word that you have chosen. If this is the case, then you can restore the wallet like this:

1. Click File -> New/Restore
2. Give a name for the wallet -> Next
3. Standard Wallet -> Next
4. I already have a seed -> Next
5. Enter your 12 word seed
6. Click "Options"
7. Check "Extend this seed with custom words" -> OK -> Next
8. Type your 1 extra word that you have chosen -> Next
9. Type a password for your new wallet -> Next
10. If the seed is correct you should have your wallet with you funds back

Also make sure you have the latest Electrum version (download only from https://electrum.org/#download)