What is the best way, can I use the Silicone Sealant, I have already cleaned the wall,
And then put a bathtub sealant trim?

By trim are you talikng about the vinyl strip with adhesive on it? I would remove that if its what you used. Get a good caulk made for baths. DAP marks one with a mildewcide built in to prevent mildew. If you are very good with caulking you can strike the joint with your finger after dipping it in soapy water.

If you can't drive a caulking gun very well you can buy at in a roll at any home store. Just peel of the paper and stick it down.