Start by reading the introduction tutorials:
https://neuroimage.usc.edu/brainstorm/Tutorials
https://neuroimage.usc.edu/brainstorm/Tutorials/ChannelFile#Review_vs_Import
Would it be better to segment the rsEEG data in 1 or 2s and calculate the sources in the averaged data rather than using the continuous file?
Not if you are following the pipeline that we document in the resting state tutorial.
But you are free to assemble the processing pipeline you want. If you are not very familiar with these measures, try not to go far away from your reference publications or well documented examples.
The "TF" structure contains the power values for each frequency in each scout, is this correct? May I ask what the "1" in the 68x1x6 struct stands for?
Introduction tutorials:
https://neuroimage.usc.edu/brainstorm/Tutorials/TimeFrequency#On_the_hard_drive
And if I want to perform connectivity analyses using FT, would I have to use this struct?
No, you are not going to run your connectivity analysis on your power spectrum, you need to process your recordings.