Hi Jacqui,
The Roman numerals in Becky's posting relate to the number of the chord in a key. A I chord is the first chord, like a C in the key of C; a IV would be an F, and a V would be a G. A ii would be a D, but because it is in lower case letters, she means a Dminor. If you know the key you want to play it in, you just slot the relevant chords in. Bonny Portmore is:
I-V-ii-IV
I-V-IV-V
ii-I-ii-IV
ii-I-IV-V.

If you were playing it in D, it would be:
D-A-Em-G
D-A-G-A
Em-D-Em-G
Em-D-G-A.


It is pretty easy to hear the places in each line where the chords change.
yours, Peter T.