To encrypt, use original message character on row and key character on column and pick where it crosses as encrypted character. Treat * and space the same, as well as O and zero, send space as *. To decrypt, use key character on row, find encrypted message character on that line and follow back to end of column to find original message character.

*ABCDEFGHIJKLMNOPQRSTUVWXYZ123456789*
ABCDEFGHIJKLMNOPQRSTUVWXYZ123456789*A
BCDEFGHIJKLMNOPQRSTUVWXYZ123456789*AB
CDEFGHIJKLMNOPQRSTUVWXYZ123456789*ABC
DEFGHIJKLMNOPQRSTUVWXYZ123456789*ABCD
EFGHIJKLMNOPQRSTUVWXYZ123456789*ABCDE
FGHIJKLMNOPQRSTUVWXYZ123456789*ABCDEF
GHIJKLMNOPQRSTUVWXYZ123456789*ABCDEFG
HIJKLMNOPQRSTUVWXYZ123456789*ABCDEFGH
IJKLMNOPQRSTUVWXYZ123456789*ABCDEFGHI
JKLMNOPQRSTUVWXYZ123456789*ABCDEFGHIJ
KLMNOPQRSTUVWXYZ123456789*ABCDEFGHIJK
LMNOPQRSTUVWXYZ123456789*ABCDEFGHIJKL
MNOPQRSTUVWXYZ123456789*ABCDEFGHIJKLM
NOPQRSTUVWXYZ123456789*ABCDEFGHIJKLMN
OPQRSTUVWXYZ123456789*ABCDEFGHIJKLMNO
PQRSTUVWXYZ123456789*ABCDEFGHIJKLMNOP
QRSTUVWXYZ123456789*ABCDEFGHIJKLMNOPQ
RSTUVWXYZ123456789*ABCDEFGHIJKLMNOPQR
STUVWXYZ123456789*ABCDEFGHIJKLMNOPQRS
TUVWXYZ123456789*ABCDEFGHIJKLMNOPQRST
UVWXYZ123456789*ABCDEFGHIJKLMNOPQRSTU
VWXYZ123456789*ABCDEFGHIJKLMNOPQRSTUV
WXYZ123456789*ABCDEFGHIJKLMNOPQRSTUVW
XYZ123456789*ABCDEFGHIJKLMNOPQRSTUVWX
YZ123456789*ABCDEFGHIJKLMNOPQRSTUVWXY
Z123456789*ABCDEFGHIJKLMNOPQRSTUVWXYZ
123456789*ABCDEFGHIJKLMNOPQRSTUVWXYZ1
23456789*ABCDEFGHIJKLMNOPQRSTUVWXYZ12
3456789*ABCDEFGHIJKLMNOPQRSTUVWXYZ123
456789*ABCDEFGHIJKLMNOPQRSTUVWXYZ1234
56789*ABCDEFGHIJKLMNOPQRSTUVWXYZ12345
6789*ABCDEFGHIJKLMNOPQRSTUVWXYZ123456
789*ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567
89*ABCDEFGHIJKLMNOPQRSTUVWXYZ12345678
9*ABCDEFGHIJKLMNOPQRSTUVWXYZ123456789
*ABCDEFGHIJKLMNOPQRSTUVWXYZ123456789*