Unable to grab and drag transitions or trimmed clips into timeline

I am new to Premiere Pro. I had used Corel Video Studio for many years but the resolution was poor. I would really like it if Adobe was as simple as the tutorials I have reviewed but I am running into a very frustrating issue. Every time I try to drag a transition or drag a trimmed clip (video only, without audio) from the source panel there is a circle with a slash icon over the hand grab. Please simply state what is the problem. I looked at other tutorial and viewed your community board and there is no solution. Please help me.