Can I download Audacity in a tablet (Android) how 
Thanks!
No. There are versions for Windows, Mac, and Linux.
You can record on your Android device (with another app) and then transfer the files to the computer for editing. Just make sure the app can record to high-quality uncompressed WAV (or other standard-lossless format). …Some people end-up with odd file formats that are difficult to convert.
You can probably find an audio editing app… There are LOTs of audio related apps, and add-on hardware, for iOS.
I wouldn’t want to edit audio on a small screen or on a system with limited storage. People doing “serious” audio work with a DAW often have two large video monitors! (And, large audio monitors.)