The steps to be taken are:

1. Insert the external reference sample.
2. TURN OFF THE LOCK (You will not see a lock signal for neat phosphoric acid and trifluoro acetic acid)
3. Write down the z0 value of the lock window.
4. Take a spectrum
5. Reference the line as indicated on the tube (for example rl(-78.5p) for trifluoroacetic acid. )
6. Insert your sample of interest. Shim, if you like. You may have to turn on the lock for shimming.
7. TURN OFF THE LOCK.
8. Set z0 to the value you wrote down.
9. Take a spectrum of your sample. It is already referenced.

If you took the spectrum of your sample first and the spectrum of the reference second things are a little more involved. Steps to take are:

1. Insert your sample of interest.
2. Shim on it if you like.
3. Write down the z0 value.
4. TURN OFF THE LOCK.
5. Take a spectrum of your sample.
6. Type mp(i,j) where i is the experiment number you are in, j the experiment number you want to take the reference spectrum in. For example mp(1,2) moves the parameters from exp1 to exp2.
7. Join your target experiment jexpj, for example jexp2
8. Eject your sample and insert the reference sample.
9. TURN OFF THE LOCK.
10. Make sure that z0 is identical to the written value (see 3)
11. Take a spectrum.
12. Reference the resonance line to the value given on the tube (for example rl(-78.5p) for trifluoroacetic acid. )
13. Type mref. You will be asked for the experiment number of the reference and of your sample. This transfers the reference information from the experiment, where you took the reference sample to the spectrum of your sample.