Can't enable Plugin Page

Hi everyone,

first time configuring and using phplist. All till now went ok, except for enabling plugin page (manage plugin).
It returns me a The plugin root directory is not writable, please install plugins manually
Please, what should I do now?

I do appreciate any guidelines.

Update!
I solve the problem myself by editing config file in config folder commenting out the proper define parameter line. Now it work as it should.