Check these FAQ published on our blog to understand the initial battery charging

We remind all users of the LFP cells and LP batteries that the cells and batteries MUST be charged to full voltage level BEFORE assembling into a pack and before starting to be used.  source

The new 3.2V LFP cells delivered from the warehouse are partially charged. However before the first use, it is essential to charge each cell to full capacity. source

The cells must be charged individually to full voltage level (typically 4.0V) before assembling the battery pack. This way the cells will be fully charged and balanced before the first use of the battery pack and there will be no need to balance the cells using the BMS with balancing. source

Using a regulated power supply is a suitable method for performing the initial charging or for the balancing of a single cell in a battery pack (by means of charging to a fixed voltage level). source

Since the battery consists of a serial string of many cells, you need to monitor each cell to prevent from deep discharge or over charge. source