Hi Heather and a very warm welcome to the community.
You have already been given so much good advice.
I went looking for the Grade 1 Module 5 C chord lesson to post some advice there and tag you - but it hasn’t been linked yet so I’ve noted that for our web dev person.
In which case I will add some more comment in here, cluttering up your Intro topic a little more … 
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 C 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 C major 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.
Make this exercise last about five minutes.
1 minute - C alone
1 minute - C & Am
1 minute - C and G
1 minute - C and D
1 minute - C alone
Practice daily and within a week you will be smashing it!
Cheers
Richard