Step 1 - retire
Step 2 - withdraw a portion as cash if you can
Step 3 - apply it to your loans
This is the only way (unless you meet some extreme hardship provision)
Rule #1 - you are receiving a benefit (outside of the SMSF) from the investment. Immediate breach of the Act. Do not pass go, do not collect $200 - quite likely become disqualified from holding a SMSF.