You did two separate indenpendent operations:
1. you removed the axle, locknuts, cone and bearings. This is needed if the axle has free-play or bearings are dry and tight.
2. removed cassette lock-ring to remove cassette cogs. This is done to change out the cogs, such as wanting higher or lower gearing-ranges.
The additional operations you'll need to do is:
3. remove freehub-body. You'll need a 10mm hex-key for this, I find the allen-sockets that fit 3/8" ratchet-wrenches to be the easiest to use.
4. then you'll need to get a replacement 7-spd freehub body:
JensenUSA has one for $15. Install it on the hub, re-install the 10mm hollow bolt.
5. Then axle & bearings and you're back on the road!
Check out this site:
Park Tool - Freehub service