Hey Ingrid,
Thank you for reaching out to us!
We are unfortunately unable to provide support through our Pre-Sales forum channel, but to help you get started, you can add the following snippet in the end of your theme’s functions.php file:
https://gist.github.com/nefeline/1d302462e9bb2891e87a226c1a775c6e
In this example your excerpt length will be changed to 300.
If you need further assistance, please head over to The Events Calendar WordPress.org.
If you have a PRO license, you can log into your account and get assistance through the PRO forums. If you need to reset your password, you can do so here. This will send an email to the account used when you initially registered for the support forums.
I hope this helps!
Cheers,
Patricia