Yes. I've used their app to start session many times. https://www.evgo.com/ev-drivers/how-to-charge-your-ev/ even talks about it.
They also support partner roaming w/ChargePoint. A ChargePoint card or app should work too. I've encountered someone who used one of those on CP to charge on EVgo.
If you plan to spend at least $7.99 on EVgo within a month, better to get a membership (https://www.evgo.com/pricing/). When I last tried, basically, you get charged the membership price. When you charge, it credits you back the amount you spent each time, until you hit $7.99. Basically, your first $7.99 of charging is included in that $7.99 you pay upfront. It's the per minute rate afterward.