I am new to this too, but here's what I did. I got the petco 6.6 gallon tank and found the filter even on low setting was a bit strong for my betta, not overly strong but enough to move him around a bit.
I 'baffled' the outflow (where the water returns to the tank from the filter) with an aquarium sponge (was like $3 from petco, got a large one and cut it to fit, used a rubber band to hold it on) theres a quick guide for baffles in this section
actually, the one about the sponge is on the fourth page of it. This cut down on him being 'pushed' around the tank.
For the inflow (where the filter sucks the water in from), which is what I believe your referring to I took some pantyhose and cut them to fit the intake area. Then pulled it over the bottom if the intake and used a rubber band to keep it on.
I did this before putting my betta in his tank, but like yours he seems to enjoy / is curious about what the intake is on the filter and likes to swim really close / circles around it until he gets 'caught', however, I think the pantyhose stop his fins from getting sucking in / damaged. I hope so anyway, hopefully someone else can chime in and confirm the pantyhose thing will stop them from hurting themselves at least.