Hi @nickc744 and welcome to the community.
You’re learning Dm so now have met six chords - A, E, D and Am, Em, Dm.
This advice is a little beyond the sort of practice Justin suggests but does tie in with what you describe that you are doing. See if it is of any help. Or store it for later as you progress.
This takes the idea you have already met and stretches it out a little to address the chord formation in songs when you need to be able to change to and from it.
To improve the Dm chord formation, try this:
- Hold your fingers near to but not touching the strings.
- Touch the fingers where the chord is but do not press.
- Once you have all three touching at the correct place then press them down.
- Do not strum - this is a fretting hand exercise only.
- Release the pressure after a few seconds but keep touching the strings.
- Then move your hand away from the strings by a small amount. All fingers away.
- Repeat the process.
Then, to improve changes to and from the Dm chord and other commonly grouped chords, repeat the above process with one alteration. After the final step of lifting all fingers away, the next cycle would be over the chord that you are changing to. Once that chord has been done and fingers are lifted away, go back to the first chord of the pair. Wash, rinse, repeat.
1 minute - Dm alone
1 minute - Dm & Am
1 minute - Dm and Em
1 minute - Dm and Am
1 minute - Dm alone
Hope that helps.
Cheers 
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