Pop ups etc keep happening & need to know how to fix the problem.?

For the last couple months I have been getting alot of unwanted pop ups, then my computer won't let me do a thing, then it does but takes awhile, won't open some things etc, etc. I am pretty illiterate when it comes to "Run it in the safe mode" cuz don't know where to find that. I did go into the Help & did what that told me, it helped for awhile but is back to alot of the pop ups etc again. Please walk me thru what to do, step by step. I have Norton as far as I know.