If you have this construction, as I + past simple e.g. said, explained,
you must also add the place or time where you explained e.g. in the previous paragraph, earlier etc.
These are some options:
As already discussed
As indicated earlier / above
As mentioned in the previous paragraph
Be careful when you use these phrases that you don't go on to repeat a previous point. Even native speakers use these kinds of expressions unnecessarily in writing.