Manually Add Custom Capabilities per User

I have read and re-read this post, and I don’t quite understand.

I am moving from a competing plugin (WPMUdev Membership). I’ve created all of my payment buttons using Level 1 and capabilities (so that subscribers can have access to more than one capability), but now I need to manually assign these capabilities to members with existing purchases on my old system.

I don’t understand how to do that. I went into php.myadmin, and I can see where the capabilities field is, but it’s a little bit gibberishy for me to manually edit.

*** A LITTLE BIT OF BACKGROUND/MY SCENARIO ***

The site I am working on, http://www.finisjhung.com/Streaming is a premium content site with streaming instructional videos.

Each video has two options: BUY NOW (AuthNet) for 3-days or BUY NOW Unlimited (non-recurring).

After reading other documentation, I decided it’s best to offer each video as its own custom capability in Level 1. My understanding/hope is that if someone purchases a second or third video, then the new capability will just be added to her account. Correct?

I am currently using WPMUdev Membership Pro, but I’ve had too many issues and am switching over to s2Member. As a result, though, I have a number of members who’ve already purchased access to some videos, and I need to grant them access to the purchase(s) they’ve already made.

THANK YOU!