Quick and dirty way is to go to cli/configure and copy/paste the following:
set poe interface all priority low maximum-power 15.4 telemetries
set poe management static guard-band 15
This will turn on all ports at power rates indicated above.
To check your PoE ports try the following in cli:
show poe interface
Result will look like:
root@ALiSRX210HE-PoE> show poe interface
Interface Admin status Oper status Max power Priority Power consumption Class
ge-0/0/0 Enabled Searching 15.4W Low 0.0W 0
ge-0/0/1 Enabled Searching 15.4W Low 0.0W 0
fe-0/0/2 Enabled Powered-up 15.4W Low 4.5W 0
fe-0/0/3 Enabled Searching 15.4W Low 0.0W 0
You can see status and power variables update frequently.