1) Go to Swap tab of the Karura App and click "Add Liquidity" in the upper ribbon. Select the pair you'd like to provide liquidity to from the dropdown. Taiga Stable pairs are denoted by the purple icon. Enter the amount of liquidity you'd like to add and then click Add Liquidity.
When adding liquidity, please note that you have the option to provide liquidity to any tokens in the pool (there is no requirement to provide liquidity to all tokens). In addition, you can provide these tokens in any ratios you see fit. You also have the option to add all assets in a balanced portion by selecting the toggle.
2) You can return to the Portfolio tab to see your Taiga LP tokens. You can track the trading volume of your pool here.