First you can set the string, which have to be on the first line of the sign in the config. Default is [RankUp]. Then you can create a sign ingame if you have the permissions CommandRank.createSign. It will look like this:
If you have Permissions to create it:
In the 2.,3. and 4. line, you can write what ever you want.
If you have not the permissions to create a sign, it looks like this: In the second line, it adds the name of the player, and it logs that the player <name> wanted to create a RankUp sign.
You can create signs with different RankUps. Then, the signs look like that:
[RankUp] group comment comment
[RankUp] Builder $500