Recording
When recording the guitar, you need to connect it as follows:
1. Guitar -> Instrument Input on interface
or
2. Guitar -> DI-box mic level -> mic preamp on interface
or
3. Guitar -> DI-box line level -> line input
...depending on what hardware you have.
Reamping
When reamping the guitar, you need to connect as follows:
Line output -> Reamp box -> Amplifier
Then you play the previously recorded audio into the line output.