Read up on using pre-compositions and animation presets to create instanciatable/ reusable data and structure your work.
I just want to know do I KNOW COPY one lower thirds for multiple use in one video , because when i try to change text in one lower third and copy same exact lower third and then change the text , the text also changes in previous lower third.
First of all After Effects is a tool designed to create visual effects shots and short sequences. If you have a video that is longer than a few seconds and you want to add lower thirds you would be better off designing the lower third as a template with editable text for use in Premiere Pro. See instructions below.
If you really want to create multiple lower thirds and add them to a video in AE here's the procedure:
- If you want your lower third to be on screen for 10 seconds create a comp the is 10 seconds long and name it something like "Lwr third 01"
- Add some sample video like a talking head to the comp to give you a reference
- Design and animate your lower third
- Delete the reference video from the comp
- Save the project as an AET (After Effects Template)
- If you have 10 lower thirds that you want to create go to the Project Panel and duplicate the "Low third 01" comp 10 times
- Open each of the 10 comps in the timeline and modify the text for each comp
- Create a new comp named something like "Main Comp" long enough to hold your final video
- Add your video to the Main Comp timeline
- Move the CTI to where you want the first lower third to start and drag the Lwr third 01 comp to the timeline lining it up with the CTI
- Move the CTI to where you want the second lower third to appear and drag Lwr third 02 into position and repeat until they are all in position
A much easier way to do this is to Follow steps 1 through 4 then go to Composition>Composition Settings and pick the Advanced tab and select Template (unlocked text layers editable in Premiere Pro)
Then save the project as an AEP file. Now add your lower thirds in Premiere Pro by dimply using the Media Browser to import your lower third template AEP, open the template comp in the Source Monitor then edit the text in Premiere Pro's Effects Control Panel, then drag the lower third from the Source Monitor to the timeline. If you've designed the lower third properly so any text you enter will animate properly then this workflow will save you a bunch of time.
Here's a tutorial that can be found by simply typing "editable text" in the Search Help field at the top right corner of AE: