Good, first of all: this is Plus! related so it should be placed in MsgPlus! Help & Support. But to answer your question: (which isn't formed in a very readable way)
Note: the following steps are for Messenger Plus! Live 4.xx in English
- Enabling Chat Logging
- Open your Plus! preferences by going to your contact list, click on the Plus! icon and select "Preferences...". You can also open them by sending the command "/prefs" or "/config" in any conversation window.
- Go to Conversations > Chat Logging
- Make sure the checkbox "Save all my chats to log files by default..." is checked.
- Optionally, you can choose where to store your log files and whether they're saved by date or by e-mail. If you want to save your logs in HTML (which saves emoticons and winks too), choose that option in "Save Options". If you only want plain text files, check the other option. Look at the other options and set them to your tastes.
- If you want to encrypt your logs, go to Conversations > Logs Encryption, check "Protect my chat logs with a password" and type a password. This password cannot be retrieved when you've forgot it and therefore you should do this only if you can remember the password or when you've written it down somewhere you know!
- Press "OK" or "Apply" to save your new settings.
- Opening a chat log
The logs are stored in the location you've set in your preferences. So, go to that folder and you can view them there by opening the .htm files. (.ple if they're encrypted)
You can also view your logs using Plus!' Chat Log Viewer. This can be accessed by opening a .ple file or by clicking on the Plus! icon in your contact list or chat window and choosing "Chat Log Viewer..." (in a conversation, "Open Chat Log..." will appear which will immediately open the log of the person you're chatting with)
EDIT: Oh yeh, you can also use Messenger's own chat logs, but those aren't that advanced as Plus!' logs.