- There's no capo in that chord diagram.
- It's not a C#m7 chord, it is a C#m7 flat five, which makes it an Em6 with C# in the bass. It says "b5" in parentheses. For the life of me I cannot understand why anyone would write it in smaller text and in parentheses, because the flat five makes all the difference and changes the whole meaning of the chord. If it was just C#m7, it would correspond to an E major chord, but now it's an E minor, totally different.
Here's a fixed version:
"Educated" jazz snobs dislike writing Em6/C#, but once again we see that beginners do not even see the "b5", let alone understand what it means. Em/C# or even just plain Em would retain the original meaning better and do less damage than C#m7 without flattening the fifth. Depending on the melody a C#m7 can sometimes work, but it also changes the mood.
The subject asks about construction, so here are the components of the chord. On the upper strings there's an E minor triad E, G, B, and then there's C# in the bass.
If we compare this to a regular C#m7 without the flat five (following a similar voicing), we see that now there's an E major triad E, G#, B, and the C# in the bass.
At the same time, there's another perspective to see C#m7-5: there's a C# diminished ("C#m-5" or flat five), and there's an added seventh
And finally, here's a different voicing for the same chord. I think this is not only easier to play, but it sounds nicer as well:
The only downside with this is, the Em shape isn't so clearly visible.
For completeness, maybe I should add that there are many different ways to write a half-diminished seventh chord as a chord symbol, e.g. C#m7-5 or C#m7♭5 or with a circle Cø7 or Cø. See https://en.wikipedia.org/wiki/Half-diminished_seventh_chord#Chord_symbols_and_terminology