You can only transfer GRX (GRAYLL) and XLM (Stellar Lumens) to your GRAYLL App account. You can transfer GRX & XLM to your GRAYLL App account from any Stellar Network account. You need to use your GRAYLL App account address, which is also referred to as the Public Key to receive transfers. Public Keys start with the letter "G" - for example: GY4S3FML4S25HDAMJYZJYAC3CKLDWV2Z6YPV3IZXOSHSQKNSKUNQFXYZ.
The GRAYLL GRX digital asset can be purchased with XLM (Stellar Lumens) in the GRAYLL App - https://app.grayll.io - XLM can be bought on - https://lobstr.co - You may also use a Visa or MasterCard. Another decentralized digital asset exchange where you can buy XLM is StellarX - https://www.stellarx.com