As described in more detail in Progressive Blues Harmonica, a "First Position" blues harmonica lick or solo is one in which the key of the harmonica is the same as the key of the song. Thus a key of C harmonica is used to produce a song or lick in the key of C.
The following First Position Blues Solo should be played first without utilizing single notes, and then with single notes. Practice playing Lick 6a, below, before attempting the entire solo.
Now play the solo, using a three note chord for each beat.
Licks 6b through 6e provide an excellent preparation for playing the Simplest First Position Blues using only single notes for each beat.