The standard grips this chord is usually shown with.
Bbm is Bb, Db and F, a minor triad. The shape this page opens on is written x13321, lowest string first.

Also written Bbmin, Bb- or Bb minor. The same chord either way; which spelling you meet depends on who wrote the chart.
There are 9 common shapes for Bbm on the guitar, and 46 derived voicings in the triad family.
In which keys. Every note of Bbm belongs to C# major (the vi), Eb minor (the v), F minor (the iv), F# major (the iii), Ab major (the ii) and Bb minor (the i).
The common shapes, written lowest string first: x13321, x4332x, 6433x6, 688666, xx8666, x-x-8-10-11-9, x-x-11-10-11-9, x-13-11-10-11-x, x-13-15-15-14-13.
Triad. Three notes across one string set. Bbm has xxx321, x1332x, xx3321, xx332x, x4332x, x433xx, xx866x, xxx666.
The common shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.